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Olsen T, Vinknes KJ, Barvíková K, Stolt E, Lee-Ødegård S, Troensegaard H, Johannessen H, Elshorbagy A, Sokolová J, Krijt J, Křížková M, Ditrói T, Nagy P, Øvrebø B, Refsum H, Thoresen M, Retterstøl K, Kožich V. Dietary sulfur amino acid restriction in humans with overweight and obesity: Evidence of an altered plasma and urine sulfurome, and a novel metabolic signature that correlates with loss of fat mass and adipose tissue gene expression. Redox Biol 2024; 73:103192. [PMID: 38776754 PMCID: PMC11163171 DOI: 10.1016/j.redox.2024.103192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 05/03/2024] [Accepted: 05/12/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND In animals, dietary sulfur amino acid restriction (SAAR) improves metabolic health, possibly mediated by altering sulfur amino acid metabolism and enhanced anti-obesogenic processes in adipose tissue. AIM To assess the effects of SAAR over time on the plasma and urine SAA-related metabolites (sulfurome) in humans with overweight and obesity, and explore whether such changes were associated with body weight, body fat and adipose tissue gene expression. METHODS Fifty-nine subjects were randomly allocated to SAAR (∼2 g SAA, n = 31) or a control diet (∼5.6 g SAA, n = 28) consisting of plant-based whole-foods and supplemented with capsules to titrate contents of SAA. Sulfurome metabolites in plasma and urine at baseline, 4 and 8 weeks were measured using HPLC and LC-MS/MS. mRNA-sequencing of subcutaneous white adipose tissue (scWAT) was performed to assess changes in gene expression. Data were analyzed with mixed model regression. Principal component analyses (PCA) were performed on the sulfurome data to identify potential signatures characterizing the response to SAAR. RESULTS SAAR led to marked decrease of the main urinary excretion product sulfate (p < 0.001) and plasma and/or 24-h urine concentrations of cystathionine, sulfite, thiosulfate, H2S, hypotaurine and taurine. PCA revealed a distinct metabolic signature related to decreased transsulfuration and H2S catabolism that predicted greater weight loss and android fat mass loss in SAAR vs. controls (all pinteraction < 0.05). This signature correlated positively with scWAT expression of genes in the tricarboxylic acid cycle, electron transport and β-oxidation (FDR = 0.02). CONCLUSION SAAR leads to distinct alterations of the plasma and urine sulfurome in humans, and predicted increased loss of weight and android fat mass, and adipose tissue lipolytic gene expression in scWAT. Our data suggest that SAA are linked to obesogenic processes and that SAAR may be useful for obesity and related disorders. TRIAL IDENTIFIER: https://clinicaltrials.gov/study/NCT04701346.
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Affiliation(s)
- Thomas Olsen
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway.
| | - Kathrine J Vinknes
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway
| | - Kristýna Barvíková
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine, and General University Hospital, Ke Karlovu 2, 128 00 Prague, Czech Republic
| | - Emma Stolt
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway
| | - Sindre Lee-Ødegård
- Department of Endocrinology, Morbid Obesity and Preventive Medicine, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Postboks 4959 Nydalen, OUS HF Aker sykehus, 0424 Oslo, Norway
| | - Hannibal Troensegaard
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway
| | - Hanna Johannessen
- Department of Pathology, Oslo University Hospital, Rikshospitalet, Postboks 45980 Nydalen, OUS HF Rikshospitalet, 0424 Oslo, Norway
| | - Amany Elshorbagy
- Department of Physiology, Faculty of Medicine, University of Alexandria, Chamblion street, Qesm Al Attarin, Alexandria 5372066, Egypt; Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford OX1 3QT, UK
| | - Jitka Sokolová
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine, and General University Hospital, Ke Karlovu 2, 128 00 Prague, Czech Republic
| | - Jakub Krijt
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine, and General University Hospital, Ke Karlovu 2, 128 00 Prague, Czech Republic
| | - Michaela Křížková
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine, and General University Hospital, Ke Karlovu 2, 128 00 Prague, Czech Republic
| | - Tamás Ditrói
- Department of Molecular Immunology and Toxicology and the National Tumor Biology Laboratory, National Institute of Oncology, Ráth György u. 7-9, 1122 Budapest, Hungary
| | - Péter Nagy
- Department of Molecular Immunology and Toxicology and the National Tumor Biology Laboratory, National Institute of Oncology, Ráth György u. 7-9, 1122 Budapest, Hungary; Department of Anatomy and Histology, HUN-REN-UVMB Laboratory of Redox Biology Research Group, University of Veterinary Medicine, 1078 Budapest, Hungary; Chemistry Institute, University of Debrecen, 4012 Debrecen, Hungary
| | - Bente Øvrebø
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway; Department of Food Safety, Norwegian Institute of Public Health, Postboks 222 Skøyen, 0213 Oslo, Norway
| | - Helga Refsum
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway; Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford OX1 3QT, UK
| | - Magne Thoresen
- Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Postboks 1122 Blindern, 0317 Oslo, Norway
| | - Kjetil Retterstøl
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine University of Oslo, Postboks 1046 Blindern, 0317 Oslo, Norway; The Lipid Clinic, Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Postboks 4959 Nydalen, OUS HF Aker sykehus, 0424 Oslo, Norway
| | - Viktor Kožich
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine, and General University Hospital, Ke Karlovu 2, 128 00 Prague, Czech Republic.
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Schultz RL, Sabat G, Fox BG, Brunold TC. A Single DNA Point Mutation Leads to the Formation of a Cysteine-Tyrosine Crosslink in the Cysteine Dioxygenase from Bacillus subtilis. Biochemistry 2023; 62:1964-1975. [PMID: 37285547 PMCID: PMC10697556 DOI: 10.1021/acs.biochem.3c00083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Cysteine dioxygenase (CDO) is a non-heme iron-containing enzyme that catalyzes the oxidation of cysteine (Cys) to cysteine sulfinic acid (CSA). Crystal structures of eukaryotic CDOs revealed the presence of an unusual crosslink between the sulfur of a cysteine residue (C93 in Mus musculus CDO, MmCDO) and a carbon atom adjacent to the phenyl group of a tyrosine residue (Y157). Formation of this crosslink occurs over time as a byproduct of catalysis and increases the catalytic efficiency of CDO by at least 10-fold. Interestingly, in bacterial CDOs, the residue corresponding to C93 is replaced by a highly conserved glycine (G82 in Bacillus subtilis CDO, BsCDO), which precludes the formation of a C-Y crosslink in these enzymes; yet bacterial CDOs achieve turnover rates paralleling those of fully crosslinked eukaryotic CDOs. In the present study, we prepared the G82C variant of BsCDO to determine if a single DNA point mutation could lead to C-Y crosslink formation in this enzyme. We used gel electrophoresis, peptide mass spectrometry, electron paramagnetic resonance spectroscopy, and kinetic assays to characterize this variant alongside the natively crosslinked wild-type (WT) MmCDO and the natively non-crosslinked WT BsCDO. Collectively, our results provide compelling evidence that the G82C BsCDO variant is indeed capable of C-Y crosslink formation. Our kinetic studies indicate that G82C BsCDO has a reduced catalytic efficiency compared to WT BsCDO and that activity increases as the ratio of crosslinked to non-crosslinked enzyme increases. Finally, by carrying out a bioinformatic analysis of the CDO family, we were able to identify a large number of putatively crosslinked bacterial CDOs, the majority of which are from Gram-negative pathogenic bacteria.
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Affiliation(s)
- Rebecca L. Schultz
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Grzegorz Sabat
- Mass Spectrometry Core, Biotechnology Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Brian G. Fox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Fernandez RL, Juntunen ND, Brunold TC. Differences in the Second Coordination Sphere Tailor the Substrate Specificity and Reactivity of Thiol Dioxygenases. Acc Chem Res 2022; 55:2480-2490. [PMID: 35994511 PMCID: PMC9583696 DOI: 10.1021/acs.accounts.2c00359] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In recent years, considerable progress has been made toward elucidating the geometric and electronic structures of thiol dioxygenases (TDOs). TDOs catalyze the conversion of substrates with a sulfhydryl group to their sulfinic acid derivatives via the addition of both oxygen atoms from molecular oxygen. All TDOs discovered to date belong to the family of cupin-type mononuclear nonheme Fe(II)-dependent metalloenzymes. While most members of this enzyme family bind the Fe cofactor by two histidines and one carboxylate side chain (2-His-1-carboxylate) to provide a monoanionic binding motif, TDOs feature a neutral three histidine (3-His) facial triad. In this Account, we present a bioinformatics analysis and multiple sequence alignment that highlight the significance of the secondary coordination sphere in tailoring the substrate specificity and reactivity among the different TDOs. These insights provide the framework within which important structural and functional features of the distinct TDOs are discussed.The best studied TDO is cysteine dioxygenase (CDO), which catalyzes the conversion of cysteine to cysteine sulfinic acid in both eukaryotes and prokaryotes. Crystal structures of resting and substrate-bound mammalian CDOs revealed two surprising structural motifs in the first- and second coordination spheres of the Fe center. The first is the presence of the abovementioned neutral 3-His facial triad that coordinates the Fe ion. The second is the existence of a covalent cross-link between the sulfur of Cys93 and an ortho carbon of Tyr157 (mouse CDO numbering scheme). While the exact role of this cross-link remains incompletely understood, various studies established that it is needed for proper substrate Cys positioning and gating solvent access to the active site. Intriguingly, bacterial CDOs lack the Cys-Tyr cross-link; yet, they are as active as cross-linked eukaryotic CDOs.The other known mammalian TDO is cysteamine dioxygenase (ADO). Initially, it was believed that ADO solely catalyzes the oxidation of cysteamine to hypotaurine. However, it has recently been shown that ADO additionally oxidizes N-terminal cysteine (Nt-Cys) peptides, which indicates that ADO may play a much more significant role in mammalian physiology than was originally anticipated. Though predicted on the basis of sequence alignment, site-directed mutagenesis, and spectroscopic studies, it was not until last year that two crystal structures, one of wild-type mouse ADO (solved by us) and the other of a variant of nickel-substituted human ADO, finally provided direct evidence that this enzyme also features a 3-His facial triad. These structures additionally revealed several features that are unique to ADO, including a putative cosubstrate O2 access tunnel that is lined by two Cys residues. Disulfide formation under conditions of high O2 levels may serve as a gating mechanism to prevent ADO from depleting organisms of Nt-Cys-containing molecules.The combination of kinetic and spectroscopic studies in conjunction with structural characterizations of TDOs has furthered our understanding of enzymatic sulfhydryl substrate regulation. In this article, we take advantage of the fact that the ADO X-ray crystal structures provided the final piece needed to compare and contrast key features of TDOs, an essential family of metalloenzymes found across all kingdoms of life.
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Affiliation(s)
- Rebeca L. Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Nicholas D. Juntunen
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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4
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Fernandez RL, Elmendorf LD, Smith RW, Bingman CA, Fox BG, Brunold TC. The Crystal Structure of Cysteamine Dioxygenase Reveals the Origin of the Large Substrate Scope of This Vital Mammalian Enzyme. Biochemistry 2021; 60:3728-3737. [PMID: 34762398 PMCID: PMC8679139 DOI: 10.1021/acs.biochem.1c00463] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the crystal structure of the mammalian non-heme iron enzyme cysteamine dioxygenase (ADO) at 1.9 Å resolution, which shows an Fe and three-histidine (3-His) active site situated at the end of a wide substrate access channel. The open approach to the active site is consistent with the recent discovery that ADO catalyzes not only the conversion of cysteamine to hypotaurine but also the oxidation of N-terminal cysteine (Nt-Cys) peptides to their corresponding sulfinic acids as part of the eukaryotic N-degron pathway. Whole-protein models of ADO in complex with either cysteamine or an Nt-Cys peptide, generated using molecular dynamics and quantum mechanics/molecular mechanics calculations, suggest occlusion of access to the active site by peptide substrate binding. This finding highlights the importance of a small tunnel that leads from the opposite face of the enzyme into the active site, providing a path through which co-substrate O2 could access the Fe center. Intriguingly, the entrance to this tunnel is guarded by two Cys residues that may form a disulfide bond to regulate O2 delivery in response to changes in the intracellular redox potential. Notably, the Cys and tyrosine residues shown to be capable of forming a cross-link in human ADO reside ∼7 Å from the iron center. As such, cross-link formation may not be structurally or functionally significant in ADO.
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Affiliation(s)
- Rebeca L. Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Laura D. Elmendorf
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Robert W. Smith
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Craig A. Bingman
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Brian G. Fox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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5
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Fernandez RL, Juntunen ND, Fox BG, Brunold TC. Spectroscopic investigation of iron(III) cysteamine dioxygenase in the presence of substrate (analogs): implications for the nature of substrate-bound reaction intermediates. J Biol Inorg Chem 2021; 26:947-955. [PMID: 34580769 PMCID: PMC8643075 DOI: 10.1007/s00775-021-01904-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 09/08/2021] [Indexed: 12/15/2022]
Abstract
Thiol dioxygenases (TDOs) are a class of metalloenzymes that oxidize various thiol-containing substrates to their corresponding sulfinic acids. Originally established by X-ray crystallography for cysteine dioxygenase (CDO), all TDOs are believed to contain a 3-histidine facial triad that coordinates the necessary Fe(II) cofactor. However, very little additional information is available for cysteamine dioxygenase (ADO), the only other mammalian TDO besides CDO. Previous spectroscopic characterizations revealed that ADO likely binds substrate cysteamine in a monodentate fashion, while a mass spectrometry study provided evidence that a thioether crosslink can form between Cys206 and Tyr208 (mouse ADO numbering). In the present study, we have used electronic absorption and electron paramagnetic resonance (EPR) spectroscopies to investigate the species formed upon incubation of Fe(III)ADO with sulfhydryl-containing substrates and the superoxide surrogates azide and cyanide. Our data reveal that azide is unable to coordinate to cysteamine-bound Fe(III)ADO, suggesting that the Fe(III) center lacks an open coordination site or azide competes with cysteamine for the same binding site. Alternatively, cyanide binds to either cysteamine- or Cys-bound Fe(III)ADO to yield a low-spin (S = 1/2) EPR signal that is distinct from that observed for cyanide/Cys-bound Fe(III)CDO, revealing differences in the active-site pockets between ADO and CDO. Finally, EPR spectra obtained for cyanide/cysteamine adducts of wild-type Fe(III)ADO and its Tyr208Phe variant are superimposable, implying that either an insignificant fraction of as-isolated wild-type enzyme is crosslinked or that formation of the thioether bond has minimal effects on the electronic structure of the iron cofactor.
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Affiliation(s)
- Rebeca L Fernandez
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Nicholas D Juntunen
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Brian G Fox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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6
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Stipanuk MH. Metabolism of Sulfur-Containing Amino Acids: How the Body Copes with Excess Methionine, Cysteine, and Sulfide. J Nutr 2020; 150:2494S-2505S. [PMID: 33000151 DOI: 10.1093/jn/nxaa094] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/28/2020] [Accepted: 03/16/2020] [Indexed: 02/06/2023] Open
Abstract
Metabolism of excess methionine (Met) to homocysteine (Hcy) by transmethylation is facilitated by the expression of methionine adenosyltransferase (MAT) I/III and glycine N-methyltransferase (GNMT) in liver, and a lack of either enzyme results in hypermethioninemia despite normal concentrations of MATII and methyltransferases other than GNMT. The further metabolism of Hcy by the transsulfuration pathway is facilitated by activation of cystathionine β-synthase (CBS) by S-adenosylmethionine (SAM) as well as the relatively high KM of CBS for Hcy. Transmethylation plus transsulfuration effects catabolism of the Met molecule along with transfer of the sulfur atom of Met to serine to synthesize cysteine (Cys). Oxidation and excretion of Met sulfur depend upon Cys catabolism and sulfur oxidation pathways. Excess Cys is oxidized by cysteine dioxygenase 1 (CDO1) and further metabolized to taurine or sulfate. Some Cys is normally metabolized by desulfhydration pathways, and the hydrogen sulfide (H2S) produced is further oxidized to sulfate. If Cys or Hcy concentrations are elevated, Cys or Hcy desulfhydration can result in excess H2S and thiosulfate production. Excess Cys or Met may also promote their limited metabolism by transamination pathways.
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Affiliation(s)
- Martha H Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
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7
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Forbes DL, Meneely KM, Chilton AS, Lamb AL, Ellis HR. The 3-His Metal Coordination Site Promotes the Coupling of Oxygen Activation to Cysteine Oxidation in Cysteine Dioxygenase. Biochemistry 2020; 59:2022-2031. [PMID: 32368901 DOI: 10.1021/acs.biochem.9b01085] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cysteine dioxygenase (CDO) structurally resembles cupin enzymes that use a 3-His/1-Glu coordination scheme. However, the glutamate ligand is substituted with a cysteine (Cys93) residue, which forms a thioether bond with tyrosine (Tyr157) under physiological conditions. The reversion variant, C93E CDO, was generated in order to reestablish the more common 3-His/1-Glu metal ligands of the cupin superfamily. This variant provides a framework for testing the structural and functional significance of Cys93 and the cross-link in CDO. Although dioxygen consumption was observed with C93E CDO, it was not coupled with l-cysteine oxidation. Substrate analogues (d-cysteine, cysteamine, and 3-mercaptopropionate) were not viable substrates for the C93E CDO variant, although they showed variable coordinations to the iron center. The structures of C93E and cross-linked and non-cross-linked wild-type CDO were solved by X-ray crystallography to 1.91, 2.49, and 2.30 Å, respectively. The C93E CDO variant had similar overall structural properties compared to cross-linked CDO; however, the iron was coordinated by a 3-His/1-Glu geometry, leaving only two coordination sites available for dioxygen and bidentate l-cysteine binding. The hydroxyl group of Tyr157 shifted in both non-cross-linked and C93E CDO, and this displacement prevented the residue from participating in substrate stabilization. Based on these results, the divergence of the metal center of cysteine dioxygenase from the 3-His/1-Glu geometry seen with many cupin enzymes was essential for effective substrate binding. The substitution of Glu with Cys in CDO allows for a third coordination site on the iron for bidentate cysteine and monodentate oxygen binding.
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Affiliation(s)
- Dianna L Forbes
- The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
| | - Kathleen M Meneely
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Annemarie S Chilton
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Audrey L Lamb
- Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66045, United States
| | - Holly R Ellis
- The Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States
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8
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Brandt U, Galant G, Meinert-Berning C, Steinbüchel A. Functional analysis of active amino acid residues of the mercaptosuccinate dioxygenase of Variovorax paradoxus B4. Enzyme Microb Technol 2018; 120:61-68. [PMID: 30396400 DOI: 10.1016/j.enzmictec.2018.09.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 08/23/2018] [Accepted: 09/20/2018] [Indexed: 01/20/2023]
Abstract
Thiol dioxygenases are non-heme mononuclear-iron proteins and belong to the cupin superfamily. In 2014, mercaptosuccinate dioxygenase (Msdo) of Variovorax paradoxus B4 was identified as another bacterial cysteine dioxygenase (Cdo) homolog catalyzing the conversion of mercaptosuccinate (MS) into succinate and sulfite. To gain further insights into potentially important amino acid residues for enzyme activity, seven enzyme variants were generated and analyzed. (i) Three variants comprised the substitution of one conserved histidine residue each by leucine, either supposed to be mandatory for coordination of the Fe(II) cofactor (H93 and H95) or to be important for substrate positioning within the active site (H163). The corresponding enzyme variants were completely inactive confirming their essential roles for enzyme activity. (ii) Mutation C100S resulted as well in an inactive enzyme demonstrating its importance for either stability or activity of the protein. (iii) For eukaryotic Cdo, a hydrogen bond network for substrate positioning was postulated, and the corresponding amino acids are basically present in Msdo. Albeit the MsdoQ64A mutation exhibited an increased Km of 0.29 mM when compared to the wildtype with 0.06 mM, it did not significantly affect the specific activity. (iv) The variant MsdoR66A showed only very low activity even when high amounts of enzyme were applied indicating that this residue might be important for catalysis. (v) No strong effect had the mutation Y165F for which a specific enzyme activity of 10.22 μmol min-1 mg-1 protein and a Km value of 0.06 mM with high similarity to those of the wildtype enzyme were obtained. This residue corresponds to Y157 of human Cdo, which is part of the catalytic triad and is supposed to be involved in substrate positioning. Apparently, another residue could fulfill this role in Msdo, since the loss of Y165 did not have a strong effect.
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Affiliation(s)
- Ulrike Brandt
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Gulsina Galant
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Christina Meinert-Berning
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
| | - Alexander Steinbüchel
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany; Environmental Science Department, King Abdulaziz University, Jeddah, Saudi Arabia.
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9
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Driggers CM, Kean KM, Hirschberger LL, Cooley RB, Stipanuk MH, Karplus PA. Structure-Based Insights into the Role of the Cys-Tyr Crosslink and Inhibitor Recognition by Mammalian Cysteine Dioxygenase. J Mol Biol 2016; 428:3999-4012. [PMID: 27477048 DOI: 10.1016/j.jmb.2016.07.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 07/15/2016] [Accepted: 07/18/2016] [Indexed: 10/21/2022]
Abstract
In mammals, the non-heme iron enzyme cysteine dioxygenase (CDO) helps regulate Cys levels through converting Cys to Cys sulfinic acid. Its activity is in part modulated by the formation of a Cys93-Tyr157 crosslink that increases its catalytic efficiency over 10-fold. Here, 21 high-resolution mammalian CDO structures are used to gain insight into how the Cys-Tyr crosslink promotes activity and how select competitive inhibitors bind. Crystal structures of crosslink-deficient C93A and Y157F variants reveal similar ~1.0-Å shifts in the side chain of residue 157, and both variant structures have a new chloride ion coordinating the active site iron. Cys binding is also different from wild-type CDO, and no Cys-persulfenate forms in the C93A or Y157F active sites at pH6.2 or 8.0. We conclude that the crosslink enhances activity by positioning the Tyr157 hydroxyl to enable proper Cys binding, proper oxygen binding, and optimal chemistry. In addition, structures are presented for homocysteine (Hcy), D-Cys, thiosulfate, and azide bound as competitive inhibitors. The observed binding modes of Hcy and D-Cys clarify why they are not substrates, and the binding of azide shows that in contrast to what has been proposed, it does not bind in these crystals as a superoxide mimic.
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Affiliation(s)
- Camden M Driggers
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Kelsey M Kean
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Lawrence L Hirschberger
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA
| | - Richard B Cooley
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
| | - Martha H Stipanuk
- Department of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA.
| | - P Andrew Karplus
- Department of Biochemistry and Biophysics, 2011 Ag & Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA.
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Fellner M, Siakkou E, Faponle AS, Tchesnokov EP, de Visser SP, Wilbanks SM, Jameson GNL. Influence of cysteine 164 on active site structure in rat cysteine dioxygenase. J Biol Inorg Chem 2016; 21:501-10. [PMID: 27193596 DOI: 10.1007/s00775-016-1360-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/07/2016] [Indexed: 11/29/2022]
Abstract
Cysteine dioxygenase is a non-heme mononuclear iron enzyme with unique structural features, namely an intramolecular thioether cross-link between cysteine 93 and tyrosine 157, and a disulfide bond between substrate L-cysteine and cysteine 164 in the entrance channel to the active site. We investigated how these posttranslational modifications affect catalysis through a kinetic, crystallographic and computational study. The enzyme kinetics of a C164S variant are identical to WT, indicating that disulfide formation at C164 does not significantly impair access to the active site at physiological pH. However, at high pH, the cysteine-tyrosine cross-link formation is enhanced in C164S. This supports the view that disulfide formation at position 164 can limit access to the active site. The C164S variant yielded crystal structures of unusual clarity in both resting state and with cysteine bound. Both show that the iron in the cysteine-bound complex is a mixture of penta- and hexa-coordinate with a water molecule taking up the final site (60 % occupancy), which is where dioxygen is believed to coordinate during turnover. The serine also displays stronger hydrogen bond interactions to a water bound to the amine of the substrate cysteine. However, the interactions between cysteine and iron appear unchanged. DFT calculations support this and show that WT and C164S have similar binding energies for the water molecule in the final site. This variant therefore provides evidence that WT also exists in an equilibrium between penta- and hexa-coordinate forms and the presence of the sixth ligand does not strongly affect dioxygen binding.
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Affiliation(s)
- Matthias Fellner
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Eleni Siakkou
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Abayomi S Faponle
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Egor P Tchesnokov
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Sigurd M Wilbanks
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Guy N L Jameson
- Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
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11
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Fellner M, Aloi S, Tchesnokov EP, Wilbanks SM, Jameson GNL. Substrate and pH-Dependent Kinetic Profile of 3-Mercaptopropionate Dioxygenase from Pseudomonas aeruginosa. Biochemistry 2016; 55:1362-71. [DOI: 10.1021/acs.biochem.5b01203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthias Fellner
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sekotilani Aloi
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Egor P. Tchesnokov
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sigurd M. Wilbanks
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Guy N. L. Jameson
- Department of Chemistry and ‡Department of
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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12
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Wenning L, Stöveken N, Wübbeler JH, Steinbüchel A. Substrate and Cofactor Range Differences of Two Cysteine Dioxygenases from Ralstonia eutropha H16. Appl Environ Microbiol 2016; 82:910-21. [PMID: 26590284 PMCID: PMC4725276 DOI: 10.1128/aem.02568-15] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 11/17/2015] [Indexed: 11/20/2022] Open
Abstract
Cysteine dioxygenases (Cdos), which catalyze the sulfoxidation of cysteine to cysteine sulfinic acid (CSA), have been extensively studied in eukaryotes because of their roles in several diseases. In contrast, only a few prokaryotic enzymes of this type have been investigated. In Ralstonia eutropha H16, two Cdo homologues (CdoA and CdoB) have been identified previously. In vivo studies showed that Escherichia coli cells expressing CdoA could convert 3-mercaptopropionate (3MP) to 3-sulfinopropionate (3SP), whereas no 3SP could be detected in cells expressing CdoB. The objective of this study was to confirm these findings and to study both enzymes in detail by performing an in vitro characterization. The proteins were heterologously expressed and purified to apparent homogeneity by immobilized metal chelate affinity chromatography (IMAC). Subsequent analysis of the enzyme activities revealed striking differences with regard to their substrate ranges and their specificities for the transition metal cofactor, e.g., CdoA catalyzed the sulfoxidation of 3MP to a 3-fold-greater extent than the sulfoxidation of cysteine, whereas CdoB converted only cysteine. Moreover, the dependency of the activities of the Cdos from R. eutropha H16 on the metal cofactor in the active center could be demonstrated. The importance of CdoA for the metabolism of the sulfur compounds 3,3'-thiodipropionic acid (TDP) and 3,3'-dithiodipropionic acid (DTDP) by further converting their degradation product, 3MP, was confirmed. Since 3MP can also function as a precursor for polythioester (PTE) synthesis in R. eutropha H16, deletion of cdoA might enable increased synthesis of PTEs.
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Affiliation(s)
- Leonie Wenning
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Nadine Stöveken
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Jan Hendrik Wübbeler
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Alexander Steinbüchel
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany Faculty of Environmental Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
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13
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Tchesnokov EP, Fellner M, Siakkou E, Kleffmann T, Martin LW, Aloi S, Lamont IL, Wilbanks SM, Jameson GNL. The cysteine dioxygenase homologue from Pseudomonas aeruginosa is a 3-mercaptopropionate dioxygenase. J Biol Chem 2015; 290:24424-37. [PMID: 26272617 PMCID: PMC4591825 DOI: 10.1074/jbc.m114.635672] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 08/02/2015] [Indexed: 02/02/2023] Open
Abstract
Thiol dioxygenation is the initial oxidation step that commits a thiol to important catabolic or biosynthetic pathways. The reaction is catalyzed by a family of specific non-heme mononuclear iron proteins each of which is reported to react efficiently with only one substrate. This family of enzymes includes cysteine dioxygenase, cysteamine dioxygenase, mercaptosuccinate dioxygenase, and 3-mercaptopropionate dioxygenase. Using sequence alignment to infer cysteine dioxygenase activity, a cysteine dioxygenase homologue from Pseudomonas aeruginosa (p3MDO) has been identified. Mass spectrometry of P. aeruginosa under standard growth conditions showed that p3MDO is expressed in low levels, suggesting that this metabolic pathway is available to the organism. Purified recombinant p3MDO is able to oxidize both cysteine and 3-mercaptopropionic acid in vitro, with a marked preference for 3-mercaptopropionic acid. We therefore describe this enzyme as a 3-mercaptopropionate dioxygenase. Mössbauer spectroscopy suggests that substrate binding to the ferrous iron is through the thiol but indicates that each substrate could adopt different coordination geometries. Crystallographic comparison with mammalian cysteine dioxygenase shows that the overall active site geometry is conserved but suggests that the different substrate specificity can be related to replacement of an arginine by a glutamine in the active site.
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Affiliation(s)
| | | | | | - Torsten Kleffmann
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Lois W Martin
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | | | - Iain L Lamont
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Sigurd M Wilbanks
- Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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14
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Kwak HC, Kim YM, Oh SJ, Kim SK. Sulfur amino acid metabolism in Zucker diabetic fatty rats. Biochem Pharmacol 2015; 96:256-66. [PMID: 26047850 DOI: 10.1016/j.bcp.2015.05.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/27/2015] [Indexed: 10/23/2022]
Abstract
The present study was aimed to investigate the metabolomics of sulfur amino acids in Zucker diabetic fatty (ZDF) rats, an obese type 2 diabetic animal model. Plasma levels of total cysteine, homocysteine and methionine, but not glutathione (GSH) were markedly decreased in ZDF rats. Hepatic methionine, homocysteine, cysteine, betaine, taurine, spermidine and spermine were also decreased. There are no significant difference in hepatic S-adenosylmethionine, S-adenosylhomocysteine, GSH, GSH disulfide, hypotaurine and putrescine between control and ZDF rats. Hepatic SAH hydrolase, betaine-homocysteine methyltransferase and methylene tetrahydrofolate reductase were up-regulated while activities of gamma-glutamylcysteine ligase and methionine synthase were decreased. The area under the curve (AUC) of methionine and methionine-d4 was not significantly different in control and ZDF rats treated with a mixture of methionine (60mg/kg) and methionine-d4 (20mg/kg). Moreover, the AUC of the increase in plasma total homocysteine was comparable between two groups, although the homocysteine concentration curve was shifted leftward in ZDF rats, suggesting that the plasma total homocysteine after the methionine loading was rapidly increased and normalized in ZDF rats. These results show that the AUC of plasma homocysteine is not responsive to the up-regulation of hepatic BHMT in ZDF rats. The present study suggests that the decrease in hepatic methionine may be responsible for the decreases in its metabolites, such as homocysteine, cysteine, and taurine in liver and consequently decreased plasma homocysteine levels.
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Affiliation(s)
- Hui Chan Kwak
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 305-764, Republic of Korea
| | - Young-Mi Kim
- College of Pharmacy, Hanyang University, Ansan, Gyeonggido 426-791, Republic of Korea
| | - Soo Jin Oh
- Bio-Evaluation Center, KRIBB, Ochang, Chungbuk, Republic of Korea
| | - Sang Kyum Kim
- College of Pharmacy, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 305-764, Republic of Korea.
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15
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A jack-of-all-trades: 2-mercaptosuccinic acid. Appl Microbiol Biotechnol 2015; 99:4545-57. [DOI: 10.1007/s00253-015-6605-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/11/2015] [Indexed: 12/16/2022]
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16
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Davies CG, Fellner M, Tchesnokov EP, Wilbanks SM, Jameson GNL. The Cys-Tyr cross-link of cysteine dioxygenase changes the optimal pH of the reaction without a structural change. Biochemistry 2014; 53:7961-8. [PMID: 25390690 DOI: 10.1021/bi501277a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme monoiron enzyme with an unusual posttranslational modification in the proximity of the ferrous iron active site. This modification, a cysteine to tyrosine thioether bond, cross-links two β-strands of the β-barrel. We have investigated its role in catalysis through a combined crystallographic and kinetic approach. The C93G variant lacks the cross-link and shows little change in structure from that of the wild type, suggesting that the cross-link does not stabilize an otherwise unfavorable conformation. A pH-dependent kinetic study shows that both cross-linked and un-cross-linked CDO are active but the optimal pH decreases with the presence of the cross-link. This result reflects the effect of the thioether bond on the pKa of Y157 and this residue's role in catalysis. At higher pH values, kcat is also higher for the cross-linked form, extending the pH range of activity. We therefore propose that the cross-link also increases activity by controlling deleterious interactions involving the thiol/ate of C93.
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Affiliation(s)
- Casey G Davies
- Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago , P.O. Box 56, Dunedin 9054, New Zealand
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17
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Li W, Pierce BS. Steady-state substrate specificity and O₂-coupling efficiency of mouse cysteine dioxygenase. Arch Biochem Biophys 2014; 565:49-56. [PMID: 25444857 DOI: 10.1016/j.abb.2014.11.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/07/2014] [Accepted: 11/11/2014] [Indexed: 11/15/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the oxygen-dependent oxidation of L-cysteine (Cys) to produce L-cysteine sulfinic acid (CSA). Sequence alignment of mammalian CDO with recently discovered thiol dioxygenase enzymes suggests that the mononuclear iron site within all enzymes in this class share a common 3-His first coordination sphere. This implies a similar mechanistic paradigm among thiol dioxygenase enzymes. Although steady-state studies were first reported for mammalian CDO over 45 years ago, detailed analysis of the specificity for alternative thiol-bearing substrates and their oxidative coupling efficiencies have not been reported for this enzyme. Assuming a similar mechanistic theme among this class of enzymes, characterization of the CDO substrate specificity may provide valuable insight into substrate-active site intermolecular during thiol oxidation. In this work, the substrate-specificity for wild-type Mus musculus CDO was investigated using NMR spectroscopy and LC-MS for a variety of thiol-bearing substrates. Tandem mass spectrometry was used to confirm dioxygenase activity for each non-native substrate investigated. Steady-state Michaelis-Menten parameters for sulfinic acid product formation and O₂-consumption were compared to establish the coupling efficiency for each reaction. In light of these results, the minimal substrate requirements for CDO catalysis and O₂-activation are discussed.
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Affiliation(s)
- Wei Li
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, TX 76019, United States
| | - Brad S Pierce
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, TX 76019, United States.
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18
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Involvement of the Cys-Tyr cofactor on iron binding in the active site of human cysteine dioxygenase. Amino Acids 2014; 47:55-63. [DOI: 10.1007/s00726-014-1843-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 09/18/2014] [Indexed: 10/24/2022]
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19
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Brandt U, Schürmann M, Steinbüchel A. Mercaptosuccinate dioxygenase, a cysteine dioxygenase homologue, from Variovorax paradoxus strain B4 is the key enzyme of mercaptosuccinate degradation. J Biol Chem 2014; 289:30800-30809. [PMID: 25228698 DOI: 10.1074/jbc.m114.579730] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The versatile thiol mercaptosuccinate has a wide range of applications, e.g. in quantum dot research or in bioimaging. Its metabolism is investigated in Variovorax paradoxus strain B4, which can utilize this compound as the sole source of carbon and sulfur. Proteomic studies of strain B4 resulted in the identification of a putative mercaptosuccinate dioxygenase, a cysteine dioxygenase homologue, possibly representing the key enzyme in the degradation of mercaptosuccinate. Therefore, the putative mercaptosuccinate dioxygenase was heterologously expressed, purified, and characterized in this study. The results clearly demonstrated that the enzyme utilizes mercaptosuccinate with concomitant consumption of oxygen. Thus, the enzyme is designated as mercaptosuccinate dioxygenase. Succinate and sulfite were verified as the final reaction products. The enzyme showed an apparent Km of 0.4 mM, and a specific activity (Vmax) of 20.0 μmol min(-1) mg(-1) corresponding to a kcat of 7.7 s(-1). Furthermore, the enzyme was highly specific for mercaptosuccinate, no activity was observed with cysteine, dithiothreitol, 2-mercaptoethanol, and 3-mercaptopropionate. These structurally related thiols did not have an inhibitory effect either. Fe(II) could clearly be identified as metal cofactor of the mercaptosuccinate dioxygenase with a content of 0.6 mol of Fe(II)/mol of enzyme. The recently proposed hypothesis for the degradation pathway of mercaptosuccinate based on proteome analyses could be strengthened in the present study. (i) Mercaptosuccinate is first converted to sulfinosuccinate by this mercaptosuccinate dioxygenase; (ii) sulfinosuccinate is spontaneously desulfinated to succinate and sulfite; and (iii) whereas succinate enters the central metabolism, sulfite is detoxified by the previously identified putative molybdopterin oxidoreductase.
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Affiliation(s)
- Ulrike Brandt
- Institute for Molecular Microbiology and Biotechnology, Westfälische Wilhelms-Universität, D-48149 Münster, Germany and
| | - Marc Schürmann
- Institute for Molecular Microbiology and Biotechnology, Westfälische Wilhelms-Universität, D-48149 Münster, Germany and
| | - Alexander Steinbüchel
- Institute for Molecular Microbiology and Biotechnology, Westfälische Wilhelms-Universität, D-48149 Münster, Germany and; Faculty of Biology, King Abdulaziz University, Jeddah, Saudi Arabia.
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20
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Fellner M, Doughty LM, Jameson GN, Wilbanks SM. A chromogenic assay of substrate depletion by thiol dioxygenases. Anal Biochem 2014; 459:56-60. [DOI: 10.1016/j.ab.2014.05.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 05/09/2014] [Accepted: 05/13/2014] [Indexed: 12/01/2022]
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21
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Song H, Her AS, Raso F, Zhen Z, Huo Y, Liu P. Cysteine oxidation reactions catalyzed by a mononuclear non-heme iron enzyme (OvoA) in ovothiol biosynthesis. Org Lett 2014; 16:2122-5. [PMID: 24684381 PMCID: PMC3998768 DOI: 10.1021/ol5005438] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Indexed: 12/22/2022]
Abstract
OvoA in ovothiol biosynthesis is a mononuclear non-heme iron enzyme catalyzing the oxidative coupling between histidine and cysteine. It can also catalyze the oxidative coupling between hercynine and cysteine, yet with a different regio-selectivity. Due to the potential application of this reaction for industrial ergothioneine production, in this study, we systematically characterized OvoA by a combination of three different assays. Our studies revealed that OvoA can also catalyze the oxidation of cysteine to either cysteine sulfinic acid or cystine. Remarkably, these OvoA-catalyzed reactions can be systematically modulated by a slight modification of one of its substrates, histidine.
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Affiliation(s)
- Heng Song
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
| | - Ampon Sae Her
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
| | - Fiona Raso
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
| | - Zhibin Zhen
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
| | - Yuda Huo
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
| | - Pinghua Liu
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachussetts 02215, United States
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22
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Li W, Blaesi EJ, Pecore MD, Crowell JK, Pierce BS. Second-sphere interactions between the C93-Y157 cross-link and the substrate-bound Fe site influence the O₂ coupling efficiency in mouse cysteine dioxygenase. Biochemistry 2013; 52:9104-19. [PMID: 24279989 DOI: 10.1021/bi4010232] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the O₂-dependent oxidation of l-cysteine (l-Cys) to produce cysteinesulfinic acid (CSA). Adjacent to the Fe site of CDO is a covalently cross-linked cysteine-tyrosine pair (C93-Y157). While several theories have been proposed for the function of the C93-Y157 pair, the role of this post-translational modification remains unclear. In this work, the steady-state kinetics and O₂/CSA coupling efficiency were measured for wild-type CDO and selected active site variants (Y157F, C93A, and H155A) to probe the influence of second-sphere enzyme-substrate interactions on catalysis. In these experiments, it was observed that both kcat and the O₂/CSA coupling efficiency were highly sensitive to the presence of the C93-Y157 cross-link and its proximity to the substrate carboxylate group. Complementary electron paramagnetic resonance (EPR) experiments were performed to obtain a more detailed understanding of the second-sphere interactions identified in O₂/CSA coupling experiments. Samples of the catalytically inactive substrate-bound Fe(III)-CDO species were treated with cyanide, resulting in a low-spin (S = ¹/₂) ternary complex. Remarkably, both the presence of the C93-Y157 pair and interactions with the Cys carboxylate group could be readily identified by perturbations to the rhombic EPR signal. Spectroscopically validated active site quantum mechanics/molecular mechanics and density functional theory computational models are provided to suggest a potential role for Y157 in the positioning of the substrate Cys in the active site and to verify the orientation of the g-tensor relative to the CDO Fe site molecular axis.
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Affiliation(s)
- Wei Li
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington , Arlington, Texas 76019, United States
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23
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Souness RJ, Kleffmann T, Tchesnokov EP, Wilbanks SM, Jameson GB, Jameson GNL. Mechanistic implications of persulfenate and persulfide binding in the active site of cysteine dioxygenase. Biochemistry 2013; 52:7606-17. [PMID: 24084026 DOI: 10.1021/bi400661a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Describing the organization of substrates and substrate analogues in the active site of cysteine dioxygenase identifies potential intermediates in this critical yet poorly understood reaction, the oxidation of cysteine to cysteine sulfinic acid. The fortuitous formation of persulfides under crystallization conditions has allowed their binding in the active site of cysteine dioxygenase to be studied. The crystal structures of cysteine persulfide and 3-mercaptopropionic acid persulfide bound to iron(II) in the active site show that binding of the persulfide occurs via the distal sulfide and, in the case of the cysteine persulfide, the amine also binds. Persulfide was detected by mass spectrometry in both the crystal and the drop, suggesting its origin is chemical rather than enzymatic. A mechanism involving the formation of the relevant disulfide from sulfide produced by hydrolysis of dithionite is proposed. In comparison, persulfenate {observed bound to cysteine dioxygenase [Simmons, C. R., et al. (2008) Biochemistry 47, 11390]} is shown through mass spectrometry to occur only in the crystal and not in the surrounding drop, suggesting that in the crystalline state the persulfenate does not lie on the reaction pathway. Stabilization of both the persulfenate and the persulfides does, however, suggest the position in which dioxygen binds during catalysis.
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Affiliation(s)
- Richard J Souness
- Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago , P.O. Box 56, Dunedin 9054, New Zealand
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24
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Driggers CM, Cooley RB, Sankaran B, Hirschberger LL, Stipanuk MH, Karplus PA. Cysteine dioxygenase structures from pH4 to 9: consistent cys-persulfenate formation at intermediate pH and a Cys-bound enzyme at higher pH. J Mol Biol 2013; 425:3121-36. [PMID: 23747973 DOI: 10.1016/j.jmb.2013.05.028] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 05/24/2013] [Accepted: 05/31/2013] [Indexed: 11/30/2022]
Abstract
Mammalian cysteine dioxygenase (CDO) is a mononuclear non-heme iron protein that catalyzes the conversion of cysteine (Cys) to cysteine sulfinic acid by an unclarified mechanism. One structural study revealed that a Cys-persulfenate (or Cys-persulfenic acid) formed in the active site, but quantum mechanical calculations have been used to support arguments that it is not an energetically feasible reaction intermediate. Here, we report a series of high-resolution structures of CDO soaked with Cys at pH values from 4 to 9. Cys binding is minimal at pH≤5 and persulfenate formation is consistently seen at pH values between 5.5 and 7. Also, a structure determined using laboratory-based X-ray diffraction shows that the persulfenate, with an apparent average O-O separation distance of ~1.8Å, is not an artifact of synchrotron radiation. At pH≥8, the active-site iron shifts from 4- to 5-coordinate, and Cys soaks reveal a complex with Cys, but no dioxygen, bound. This 'Cys-only' complex differs in detail from a previously published 'Cys-only' complex, which we reevaluate and conclude is not reliable. The high-resolution structures presented here do not resolve the CDO mechanism but do imply that an iron-bound persulfenate (or persulfenic acid) is energetically accessible in the CDO active site, and that CDO active-site chemistry in the crystals is influenced by protonation/deprotonation events with effective pKa values near ~5.5 and ~7.5 that influence Cys binding and oxygen binding/reactivity, respectively. Furthermore, this work provides reliable ligand-bound models for guiding future mechanistic considerations.
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Affiliation(s)
- Camden M Driggers
- Department of Biochemistry and Biophysics, 2011 Ag and Life Sciences Building, Oregon State University, Corvallis, OR 97331, USA
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25
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Buongiorno D, Straganz GD. Structure and function of atypically coordinated enzymatic mononuclear non-heme-Fe(II) centers. Coord Chem Rev 2013; 257:541-563. [PMID: 24850951 PMCID: PMC4019311 DOI: 10.1016/j.ccr.2012.04.028] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Revised: 04/17/2012] [Accepted: 04/18/2012] [Indexed: 11/17/2022]
Abstract
Mononuclear, non-heme-Fe(II) centers are key structures in O2 metabolism and catalyze an impressive variety of enzymatic reactions. While most are bound via two histidines and a carboxylate, some show a different organization. A short overview of atypically coordinated O2 dependent mononuclear-non-heme-Fe(II) centers is presented here Enzymes with 2-His, 3-His, 3-His-carboxylate and 4-His bound Fe(II) centers are discussed with a focus on their reactivity, metal ion promiscuity and recent progress in the elucidation of their enzymatic mechanisms. Observations concerning these and classically coordinated Fe(II) centers are used to understand the impact of the metal binding motif on catalysis.
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Key Words
- 1,3-bis(2-pyridylimino)isoindoline, ind
- 2OH-1,3-Ph2PD, 2-hydroxy-1,3-diphenylpropanedione
- 6-Ph2TPA, N,N-bis[(6-phenyl-2-pyridyl)methyl]-N-[(2-pyridyl)-methyl]amine
- ADO, cysteamine dioxygenase
- AO, apocarotenoid 15,15′-oxygenase
- ARD, aci-reductone dioxygenase
- BsQDO, quercetin 2,3-dioxygenase from Bacillus subtilis
- CD, circular dichroism
- CDO, cysteine dioxygenase
- CGDO, 5-chloro-gentisate 1,2-dioxygenase
- CS2, clavaminate synthase
- CarOs, carotenoid oxygenases
- DFT, density functional theory
- Dioxygen activation
- Dioxygenase
- Dke1, diketone dioxygenase
- EPR, electron paramagnetic resonance
- EXAFS, extended X-ray absorption fine structure spectroscopy
- Enzyme catalysis
- Facial triad
- GDO, gentisate 1,2-dioxygenase
- HADO, 3-hydroxyanthranilate 3,4-dioxygenase
- HGDO, homogentisate 1,2-dioxygenase
- HNDO, hydroxy-2-naphthoate dioxygenase
- MCD, magnetic circular dichroism
- MNHEs, mononuclear non-heme-Fe(II) dependent enzymes
- Metal binding motif
- NRP, nonribosomal peptide
- OTf-, trifluormethanesulfonate
- PDB, protein data bank
- QDO, quercetin 2,3-dioxygenase
- SDO, salicylate 1,2-dioxygenase
- Structure–function relationships
- TauD, taurine hydroxylase
- XAS, X-ray absorption spectroscopy
- acac, acetylacetone (2,4-pentanedione)
- fla, flavonolate
- α-KG, α-ketoglutarate
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Affiliation(s)
- Daniela Buongiorno
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12 A-8010 Graz, Austria
| | - Grit D Straganz
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12 A-8010 Graz, Austria
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Imsand EM, Njeri CW, Ellis HR. Addition of an external electron donor to in vitro assays of cysteine dioxygenase precludes the need for exogenous iron. Arch Biochem Biophys 2012; 521:10-7. [PMID: 22433531 DOI: 10.1016/j.abb.2012.03.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/03/2012] [Accepted: 03/05/2012] [Indexed: 11/19/2022]
Abstract
Cysteine dioxygenase (CDO) utilizes a 3-His facial triad for coordination of its metal center. Recombinant CDO present in cellular lysate exists primarily in the ferrous form and exhibits significant catalytic activity. Removal of CDO from the reducing cellular environment during purification results in the loss of bound iron and oxidation of greater than 99% of the remaining metal centers. The as-isolated recombinant enzyme has comparable activity as the background level of L-cysteine oxidation confirming that CDO is inactive under the aerobic conditions required for catalysis. Including exogenous ferrous iron in assays resulted in non-enzymatic product formation; however, addition of an external reductant in assays of the purified protein resulted in the recovery of CDO activity. EPR spectroscopy of CDO in the presence of a reductant confirms that the recovered activity is consistent with reduction of iron to the ferrous form. The as-isolated enzyme in the presence of L-cysteine was nearly unreactive with the dioxygen analog, but had increased affinity when pre-incubated with an external reductant. These studies shed light on the discrepancies among reported kinetic parameters for CDO and also juxtapose the stability of the 3-His and 2-His/1-carboxylate ferrous enzymes in the presence of dioxygen.
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Affiliation(s)
- Erin M Imsand
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849, USA
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Tchesnokov EP, Wilbanks SM, Jameson GNL. A Strongly Bound High-Spin Iron(II) Coordinates Cysteine and Homocysteine in Cysteine Dioxygenase. Biochemistry 2011; 51:257-64. [DOI: 10.1021/bi201597w] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Egor P. Tchesnokov
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Sigurd M. Wilbanks
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Guy N. L. Jameson
- Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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28
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Crawford JA, Li W, Pierce BS. Single turnover of substrate-bound ferric cysteine dioxygenase with superoxide anion: enzymatic reactivation, product formation, and a transient intermediate. Biochemistry 2011; 50:10241-53. [PMID: 21992268 DOI: 10.1021/bi2011724] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the O(2)-dependent oxidation of L-cysteine (Cys) to produce cysteine sulfinic acid (CSA). In this study we demonstrate that the catalytic cycle of CDO can be "primed" by one electron through chemical oxidation to produce CDO with ferric iron in the active site (Fe(III)-CDO, termed 2). While catalytically inactive, the substrate-bound form of Fe(III)-CDO (2a) is more amenable to interrogation by UV-vis and EPR spectroscopy than the 'as-isolated' Fe(II)-CDO enzyme (1). Chemical-rescue experiments were performed in which superoxide (O(2)(•-)) anions were introduced to 2a to explore the possibility that a Fe(III)-superoxide species represents the first intermediate within the catalytic pathway of CDO. In principle, O(2)(•-) can serve as a suitable acceptor for the remaining 3-electrons necessary for CSA formation and regeneration of the active Fe(II)-CDO enzyme (1). Indeed, addition of O(2)(•-) to 2a resulted in the rapid formation of a transient species (termed 3a) observable at 565 nm by UV-vis spectroscopy. The subsequent decay of 3a is kinetically matched to CSA formation. Moreover, a signal attributed to 3a was also identified using parallel mode X-band EPR spectroscopy (g ~ 11). Spectroscopic simulations, observed temperature dependence, and the microwave power saturation behavior of 3a are consistent with a ground state S = 3 from a ferromagnetically coupled (J ~ -8 cm(-1)) high-spin ferric iron (S(A) = 5/2) with a bound radical (S(B) = 1/2), presumably O(2)(•-). Following treatment with O(2)(•-), the specific activity of recovered CDO increased to ~60% relative to untreated enzyme.
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Affiliation(s)
- Joshua A Crawford
- Department of Chemistry and Biochemistry, College of Sciences, The University of Texas at Arlington, Arlington, Texas 76019, United States
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29
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Siakkou E, Rutledge MT, Wilbanks SM, Jameson GNL. Correlating crosslink formation with enzymatic activity in cysteine dioxygenase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:2003-9. [PMID: 21839860 DOI: 10.1016/j.bbapap.2011.07.019] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/15/2011] [Accepted: 07/21/2011] [Indexed: 10/17/2022]
Abstract
Cysteine dioxygenase (CDO) from rat and other mammals exhibits a covalent post-translational modification between the residues C93 and Y157 that is in close proximity to the active site, and whose presence enhances the enzyme's activity. Protein with and without C93-Y157 crosslink migrates as distinct bands in SDS-PAGE, allowing quantification of the relative ratios between the two forms by densitometry of the respective bands. Expression of recombinant rat wild type CDO in Escherichia coli typically produces 40-50% with the C93-Y157 crosslink. A strategy was developed to increase the ratio of the non-crosslinked form in an enzyme preparation of reasonable quantity and purity, allowing direct assessment of the activity of non-crosslinked CDO and mechanism of formation of the crosslink. The presence of ferrous iron and oxygen is a prerequisite for C93-Y157 crosslink formation. Absence of oxygen during protein expression increased the fraction of non-crosslinked CDO, while presence of the metal chelator EDTA had little effect. Metal affinity chromatography was used to enrich non-crosslinked content. Both the enzymatic rate of cysteine oxidation and the amount of cross-linking between C93 and Y157 increased significantly upon exposure of CDO to air/oxygen and substrate cysteine in the presence of iron in a hitherto unreported two-phase process. The instantaneous activity was proportional to the amount of crosslinked enzyme present, demonstrating that the non-crosslinked form has negligible enzymatic activity. The biphasic kinetics suggest the existence of an as yet uncharacterised intermediate in crosslink formation and enzyme activation.
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Affiliation(s)
- Eleni Siakkou
- Department of Chemistry, University of Otago, Dunedin, New Zealand
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Stipanuk MH, Ueki I. Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur. J Inherit Metab Dis 2011; 34:17-32. [PMID: 20162368 PMCID: PMC2901774 DOI: 10.1007/s10545-009-9006-9] [Citation(s) in RCA: 303] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/22/2009] [Accepted: 09/24/2009] [Indexed: 11/30/2022]
Abstract
Synthesis of cysteine as a product of the transsulfuration pathway can be viewed as part of methionine or homocysteine degradation, with cysteine being the vehicle for sulfur conversion to end products (sulfate, taurine) that can be excreted in the urine. Transsulfuration is regulated by stimulation of cystathionine β-synthase and inhibition of methylene tetrahydrofolate reductase in response to changes in the level of S-adenosylmethionine, and this promotes homocysteine degradation when methionine availability is high. Cysteine is catabolized by several desulfuration reactions that release sulfur in a reduced oxidation state, generating sulfane sulfur or hydrogen sulfide (H₂S), which can be further oxidized to sulfate. Cysteine desulfuration is accomplished by alternate reactions catalyzed by cystathionine β-synthase and cystathionine γ-lyase. Cysteine is also catabolized by pathways that require the initial oxidation of the cysteine thiol by cysteine dioxygenase to form cysteinesulfinate. The oxidative pathway leads to production of taurine and sulfate in a ratio of approximately 2:1. Relative metabolism of cysteine by desulfuration versus oxidative pathways is influenced by cysteine dioxygenase activity, which is low in animals fed low-protein diets and high in animals fed excess sulfur amino acids. Thus, desulfuration reactions dominate when cysteine is deficient, whereas oxidative catabolism dominates when cysteine is in excess. In rats consuming a diet with an adequate level of sulfur amino acids, about two thirds of cysteine catabolism occurs by oxidative pathways and one third by desulfuration pathways. Cysteine dioxygenase is robustly regulated in response to cysteine availability and may function to provide a pathway to siphon cysteine to less toxic metabolites than those produced by cysteine desulfuration reactions.
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Affiliation(s)
- Martha H. Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Iori Ueki
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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31
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Kasperova A, Kunert J, Horynova M, Weigl E, Sebela M, Lenobel R, Raska M. Isolation of recombinant cysteine dioxygenase protein from Trichophyton mentagrophytes. Mycoses 2010; 54:e456-62. [PMID: 21039937 DOI: 10.1111/j.1439-0507.2010.01948.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cysteine dioxygenase (CDO, EC 1.13.11.20) catalyses the oxygenation of cysteine to cysteine sulphinic acid leading to the production of sulphite, sulphate and taurine as the final metabolites of cysteine catabolism. Keratinolytic fungi secrete sulphite and sulphate to reduce disulphide bridges in host tissue keratin proteins as the first step of keratinolysis. In the present study, we describe the identification of cDNA, as well as expression and characterisation of recombinant CDO protein from Trichophyton mentagrophytes. The cDNA was amplified using primers designed on the basis of high conservancy CDO regions identified in other fungi. PCR product was cloned and sequenced. Recombinant CDO was expressed in Escherichia coli, and affinity purified and identified by matrix-assisted laser desorption/ionization - time-of-flight mass spectrometry (MALDI-TOF MS). Enzyme activity was assayed by monitoring the production of cysteine sulphinate using mass spectrometry. The Cdo cDNA encodes for a protein consisting of 219 amino acids. Recombinant CDO protein C-terminally fused with a His tag was purified by affinity chromatography. The CDO purified under native condition was proved to be enzymatically active. Protein identity was confirmed by MALDI-TOF MS. Comparison of cDNA sequence with those identified in other fungi revealed significant homology. Identification of T. mentagrophytes CDO provides indispensable tools for future studies of dermatophyte pathogenicity and development of new approaches for prevention and therapy.
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Affiliation(s)
- Alena Kasperova
- Department of Immunology, Faculty of Medicine and Dentistry, Palacky University in Olomouc, Czech Republic
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32
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Gardner JD, Pierce BS, Fox BG, Brunold TC. Spectroscopic and computational characterization of substrate-bound mouse cysteine dioxygenase: nature of the ferrous and ferric cysteine adducts and mechanistic implications. Biochemistry 2010; 49:6033-41. [PMID: 20397631 DOI: 10.1021/bi100189h] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cysteine dioxygenase (CDO) is a mononuclear non-heme Fe-dependent dioxygenase that catalyzes the initial step of oxidative cysteine catabolism. Its active site consists of an Fe(II) ion ligated by three histidine residues from the protein, an interesting variation on the more common 2-His-1-carboxylate motif found in many other non-heme Fe(II)-dependent enzymes. Multiple structural and kinetic studies of CDO have been carried out recently, resulting in a variety of proposed catalytic mechanisms; however, many open questions remain regarding the structure/function relationships of this vital enzyme. In this study, resting and substrate-bound forms of CDO in the Fe(II) and Fe(III) states, both of which are proposed to have important roles in this enzyme's catalytic mechanism, were characterized by utilizing various spectroscopic methods. The nature of the substrate/active site interactions was also explored using the cysteine analogue selenocysteine (Sec). Our electronic absorption, magnetic circular dichroism, and resonance Raman data exhibit features characteristic of direct S (or Se) ligation to both the high-spin Fe(II) and Fe(III) active site ions. The resulting Cys- (or Sec-) bound species were modeled and further characterized using density functional theory computations to generate experimentally validated geometric and electronic structure descriptions. Collectively, our results yield a more complete description of several catalytically relevant species and provide support for a reaction mechanism similar to that established for many structurally related 2-His-1-carboxylate Fe(II)-dependent dioxygenases.
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Affiliation(s)
- Jessica D Gardner
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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33
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Siakkou E, Wilbanks SM, Jameson GNL. Simplified cysteine dioxygenase activity assay allows simultaneous quantitation of both substrate and product. Anal Biochem 2010; 405:127-31. [PMID: 20541514 DOI: 10.1016/j.ab.2010.06.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/03/2010] [Accepted: 06/06/2010] [Indexed: 10/19/2022]
Abstract
A high-performance liquid chromatography (HPLC) method for enzyme activity assays using a hydrophilic interaction liquid chromatography (HILIC) column in combination with an evaporative light scattering detector was developed. The method was used to measure the activity of the non-heme mono-iron enzyme cysteine dioxygenase. The substrate cysteine and the product cysteine sulfinic acid are very weak chromophores, making direct ultraviolet (UV) detection without derivatization rather insensitive; moreover, derivatization of cysteine is often not efficient. Using the system described, underivatized substrate and product in samples from cysteine dioxygenase activity assays could be separated and analyzed. Furthermore, it was possible to quantify cysteic acid, the noncatalytic oxidation product of cysteine sulfinic acid. Acetone was used both to stop the enzymatic reaction by protein precipitation and as an organic mobile phase, making sample preparation very easy and the assay highly reproducible.
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Affiliation(s)
- Eleni Siakkou
- Department of Chemistry, University of Otago, Dunedin 9054, New Zealand
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34
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Stipanuk MH, Simmons CR, Karplus PA, Dominy JE. Thiol dioxygenases: unique families of cupin proteins. Amino Acids 2010; 41:91-102. [PMID: 20195658 DOI: 10.1007/s00726-010-0518-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 02/05/2010] [Indexed: 01/26/2023]
Abstract
Proteins in the cupin superfamily have a wide range of biological functions in archaea, bacteria and eukaryotes. Although proteins in the cupin superfamily show very low overall sequence similarity, they all contain two short but partially conserved cupin sequence motifs separated by a less conserved intermotif region that varies both in length and amino acid sequence. Furthermore, these proteins all share a common architecture described as a six-stranded β-barrel core, and this canonical cupin or "jelly roll" β-barrel is formed with cupin motif 1, the intermotif region, and cupin motif 2 each forming two of the core six β-strands in the folded protein structure. The recently obtained crystal structures of cysteine dioxygenase (CDO), with contains conserved cupin motifs, show that it has the predicted canonical cupin β-barrel fold. Although there had been no reports of CDO activity in prokaryotes, we identified a number of bacterial cupin proteins of unknown function that share low similarity with mammalian CDO and that conserve many residues in the active-site pocket of CDO. Putative bacterial CDOs predicted to have CDO activity were shown to have similar substrate specificity and kinetic parameters as eukaryotic CDOs. Information gleaned from crystal structures of mammalian CDO along with sequence information for homologs shown to have CDO activity facilitated the identification of a CDO family fingerprint motif. One key feature of the CDO fingerprint motif is that the canonical metal-binding glutamate residue in cupin motif 1 is replaced by a cysteine (in mammalian CDOs) or by a glycine (bacterial CDOs). The recent report that some putative bacterial CDO homologs are actually 3-mercaptopropionate dioxygenases suggests that the CDO family may include proteins with specificities for other thiol substrates. A paralog of CDO in mammals was also identified and shown to be the other mammalian thiol dioxygenase, cysteamine dioxygenase (ADO). A tentative fingerprint motif for ADOs, or DUF1637 family members, is proposed. In ADOs, the conserved glutamate residue in cupin motif 1 is replaced by either glycine or valine. Both ADOs and CDOs appear to represent unique clades within the cupin superfamily.
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Affiliation(s)
- Martha H Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
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Kleffmann T, Jongkees SAK, Fairweather G, Wilbanks SM, Jameson GNL. Mass-spectrometric characterization of two posttranslational modifications of cysteine dioxygenase. J Biol Inorg Chem 2009; 14:913-21. [DOI: 10.1007/s00775-009-0504-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 04/06/2009] [Indexed: 12/01/2022]
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Stipanuk MH, Ueki I, Dominy JE, Simmons CR, Hirschberger LL. Cysteine dioxygenase: a robust system for regulation of cellular cysteine levels. Amino Acids 2008; 37:55-63. [PMID: 19011731 DOI: 10.1007/s00726-008-0202-y] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 10/07/2008] [Indexed: 11/26/2022]
Abstract
Cysteine catabolism in mammals is dependent upon cysteine dioxygenase (CDO), an enzyme that adds molecular oxygen to the sulfur of cysteine, converting the thiol to a sulfinic acid known as cysteinesulfinic acid (3-sulfinoalanine). CDO is one of the most highly regulated metabolic enzymes responding to diet that is known. It undergoes up to 45-fold changes in concentration and up to 10-fold changes in catalytic efficiency. This provides a remarkable responsiveness of the cell to changes in sulfur amino acid availability: the ability to decrease CDO activity and conserve cysteine when cysteine is scarce and to rapidly increase CDO activity and catabolize cysteine to prevent cytotoxicity when cysteine supply is abundant. CDO in both liver and adipose tissues responds to changes in dietary intakes of protein and/or sulfur amino acids over a range that encompasses the requirement level, suggesting that cysteine homeostasis is very important to the living organism.
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Affiliation(s)
- M H Stipanuk
- Division of Nutritional Sciences, Cornell University, 227 Savage Hall, Ithaca, NY 14853, USA.
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Stipanuk MH, Dominy JE, Ueki I, Hirschberger LL. Measurement of Cysteine Dioxygenase Activity and Protein Abundance. ACTA ACUST UNITED AC 2008; 38:6.15.1-6.15.25. [PMID: 19885389 DOI: 10.1002/0471140856.tx0615s38] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cysteine dioxygenase is an iron (Fe(2+))-dependent thiol dioxygenase that uses molecular oxygen to oxidize the sulfhydryl group of cysteine to generate 3-sulfinoalanine (commonly called cysteinesulfinic acid). Cysteine dioxygenase activity is routinely assayed by measuring cysteinesulfinate formation from substrate L-cysteine at pH 6.1 in the presence of ferrous ions to saturate the enzyme with metal cofactor, a copper chelator to diminish substrate oxidation, and hydroxylamine to inhibit pyridoxal 5'-phosphate-dependent degradation of product. The amount of cysteine dioxygenase may be measured by immunoblotting. Upon SDS-PAGE, cysteine dioxygenase can be separated into two major bands, with the upper band representing the 23-kDa protein and the lower band representing the mature enzyme that has undergone formation of an internal thioether cross link in the active site. Formation of this cross link is dependent upon the catalytic turnover of substrate and produces an enzyme with a higher catalytic efficiency and catalytic half-life.
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Affiliation(s)
- Martha H Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853
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38
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Dominy JE, Hwang J, Guo S, Hirschberger LL, Zhang S, Stipanuk MH. Synthesis of amino acid cofactor in cysteine dioxygenase is regulated by substrate and represents a novel post-translational regulation of activity. J Biol Chem 2008; 283:12188-201. [PMID: 18308719 DOI: 10.1074/jbc.m800044200] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine dioxygenase (CDO) catalyzes the conversion of cysteine to cysteinesulfinic acid and is important in the regulation of intracellular cysteine levels in mammals and in the provision of oxidized cysteine metabolites such as sulfate and taurine. Several crystal structure studies of mammalian CDO have shown that there is a cross-linked cofactor present in the active site of the enzyme. The cofactor consists of a thioether bond between the gamma-sulfur of residue cysteine 93 and the aromatic side chain of residue tyrosine 157. The exact requirements for cofactor synthesis and the contribution of the cofactor to the catalytic activity of the enzyme have yet to be fully described. In this study, therefore, we explored the factors necessary for cofactor biogenesis in vitro and in vivo and examined what effect cofactor formation had on activity in vitro. Like other cross-linked cofactor-containing enzymes, formation of the Cys-Tyr cofactor in CDO required a transition metal cofactor (Fe(2+)) and O(2). Unlike other enzymes, however, biogenesis was also strictly dependent upon the presence of substrate. Cofactor formation was also appreciably slower than the rates reported for other enzymes and, indeed, took hundreds of catalytic turnover cycles to occur. In the absence of the Cys-Tyr cofactor, CDO possessed appreciable catalytic activity, suggesting that the cofactor was not essential for catalysis. Nevertheless, at physiologically relevant cysteine concentrations, cofactor formation increased CDO catalytic efficiency by approximately 10-fold. Overall, the regulation of Cys-Tyr cofactor formation in CDO by ambient cysteine levels represents an unusual form of substrate-mediated feed-forward activation of enzyme activity with important physiological consequences.
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Affiliation(s)
- John E Dominy
- Department of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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Phillips GN, Fox BG, Markley JL, Volkman BF, Bae E, Bitto E, Bingman CA, Frederick RO, McCoy JG, Lytle BL, Pierce BS, Song J, Twigger SN. Structures of proteins of biomedical interest from the Center for Eukaryotic Structural Genomics. ACTA ACUST UNITED AC 2007; 8:73-84. [PMID: 17786587 DOI: 10.1007/s10969-007-9023-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 07/17/2007] [Indexed: 12/01/2022]
Abstract
The Center for Eukaryotic Structural Genomics (CESG) produces and solves the structures of proteins from eukaryotes. We have developed and operate a pipeline to both solve structures and to test new methodologies. Both NMR and X-ray crystallography methods are used for structure solution. CESG chooses targets based on sequence dissimilarity to known structures, medical relevance, and nominations from members of the scientific community. Many times proteins qualify in more than one of these categories. Here we review some of the structures that have connections to human health and disease.
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Affiliation(s)
- George N Phillips
- Center for Eukaryotic Structural Genomics, Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
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40
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Pierce BS, Gardner JD, Bailey LJ, Brunold TC, Fox BG. Characterization of the nitrosyl adduct of substrate-bound mouse cysteine dioxygenase by electron paramagnetic resonance: electronic structure of the active site and mechanistic implications. Biochemistry 2007; 46:8569-78. [PMID: 17602574 DOI: 10.1021/bi700662d] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian cysteine dioxygenase (CDO) is a non-heme iron metalloenzyme that catalyzes the first committed step in oxidative cysteine catabolism. The active site coordination of CDO comprises a mononuclear iron ligated by the Nepsilon atoms of three protein-derived histidines, thus representing a new variant on the 2-histidine-1-carboxylate (2H1C) facial triad motif. Nitric oxide was used as a spectroscopic probe in investigating the order of substrate-O2 binding by EPR spectroscopy. In these experiments, CDO exhibits an ordered binding of l-cysteine prior to NO (and presumably O2) similar to that observed for the 2H1C class of non-heme iron enzymes. Moreover, the CDO active site is essentially unreactive toward NO in the absence of substrate, suggesting an obligate ordered binding of l-cysteine prior to NO. Typically, addition of NO to a mononuclear non-heme iron center results in the formation of an {FeNO}7 (S = 3/2) species characterized by an axial EPR spectrum with gx, gy, and gz values of approximately 4, approximately 4, and approximately 2, respectively. However, upon addition of NO to CDO in the presence of substrate l-cysteine, a low-spin {FeNO}7 (S = 1/2) signal that accounts for approximately 85% of the iron within the enzyme develops. Similar {FeNO}7 (S = 1/2) EPR signals have been observed for a variety of octahedral mononuclear iron-nitrosyl synthetic complexes; however, this type of iron-nitrosyl species is not commonly observed for non-heme iron enzymes. Substitution of l-cysteine with isosteric substrate analogues cysteamine, 3-mercaptopropionic acid, and propane thiol did not produce any analogous {FeNO}7 signals (S = 1/2 or 3/2), thus reflecting the high substrate specificity of the enzyme observed by a number of researchers. The unusual {FeNO}7 (S = 1/2) electronic configuration adopted by the substrate-bound iron-nitrosyl CDO (termed {ES-NO}7) is a result of the bidentate thiol/amine coordination of l-cysteine in the NO-bound CDO active site. DFT computations were performed to further characterize this species. The DFT-predicted geometric parameters for {ES-NO}7 are in good agreement with the crystallographically determined substrate-bound active site configuration of CDO and are consistent with known iron-nitrosyl model complexes. Moreover, the computed EPR parameters (g and A values) are in excellent agreement with experimental results for this CDO species and those obtained from comparable synthetic {FeNO}7 (S = 1/2) iron-nitrosyl complexes.
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Affiliation(s)
- Brad S Pierce
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, Wisconsin 53706, USA.
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Dominy JE, Simmons CR, Hirschberger LL, Hwang J, Coloso RM, Stipanuk MH. Discovery and characterization of a second mammalian thiol dioxygenase, cysteamine dioxygenase. J Biol Chem 2007; 282:25189-98. [PMID: 17581819 DOI: 10.1074/jbc.m703089200] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There are only two known thiol dioxygenase activities in mammals, and they are ascribed to the enzymes cysteine dioxygenase (CDO) and cysteamine (2-aminoethanethiol) dioxygenase (ADO). Although many studies have been dedicated to CDO, resulting in the identification of its gene and even characterization of the tertiary structure of the protein, relatively little is known about cysteamine dioxygenase. The failure to identify the gene for this protein has significantly hampered our understanding of the metabolism of cysteamine, a product of the constitutive degradation of coenzyme A, and the synthesis of taurine, the final product of cysteamine oxidation and the second most abundant amino acid in mammalian tissues. In this study we identified a hypothetical murine protein homolog of CDO (hereafter called ADO) that is encoded by the gene Gm237 and belongs to the DUF1637 protein family. When expressed as a recombinant protein, ADO exhibited significant cysteamine dioxygenase activity in vitro. The reaction was highly specific for cysteamine; cysteine was not oxidized by the enzyme, and structurally related compounds were not competitive inhibitors of the reaction. When overexpressed in HepG2/C3A cells, ADO increased the production of hypotaurine from cysteamine. Similarly, when endogenous expression of the human ADO ortholog C10orf22 in HepG2/C3A cells was reduced by RNA-mediated interference, hypotaurine production decreased. Western blots of murine tissues with an antibody developed against ADO showed that the protein is ubiquitously expressed with the highest levels in brain, heart, and skeletal muscle. Overall, these data suggest that ADO is responsible for endogenous cysteamine dioxygenase activity.
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Affiliation(s)
- John E Dominy
- Department of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
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Zhao D, McIntosh M, Fein H, Zhang X. Comparison of Methionine α,γ-Lyase and Homocysteine α,γ-Lyase for Electrochemical Determination of Homocysteine. ELECTROANAL 2007. [DOI: 10.1002/elan.200603824] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Ye S, Wu X, Wei L, Tang D, Sun P, Bartlam M, Rao Z. An Insight into the Mechanism of Human Cysteine Dioxygenase. J Biol Chem 2007; 282:3391-402. [PMID: 17135237 DOI: 10.1074/jbc.m609337200] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine dioxygenase is a non-heme mononuclear iron metalloenzyme that catalyzes the oxidation of cysteine to cysteine sulfinic acid with addition of molecular dioxygen. This irreversible oxidative catabolism of cysteine initiates several important metabolic pathways related to diverse sulfurate compounds. Cysteine dioxygenase is therefore very important for maintaining the proper hepatic concentration of intracellular free cysteine. Mechanisms for mouse and rat cysteine dioxygenases have recently been reported based on their crystal structures in the absence of substrates, although there is still a lack of direct evidence. Here we report the first crystal structure of human cysteine dioxygenase in complex with its substrate L-cysteine to 2.7A, together with enzymatic activity and metal content assays of several single point mutants. Our results provide an insight into a new mechanism of cysteine thiol dioxygenation catalyzed by cysteine dioxygenase, which is tightly associated with a thioether-bonded tyrosine-cysteine cofactor involving Tyr-157 and Cys-93. This cross-linked protein-derived cofactor plays several key roles different from those in galactose oxidase. This report provides a new potential target for therapy of diseases related to human cysteine dioxygenase, including neurodegenerative and autoimmune diseases.
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Affiliation(s)
- Sheng Ye
- Tsinghua-IBP Joint Research Group for Structural Biology, Tsinghua University, Beijing 100084, China
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Dominy JE, Simmons CR, Karplus PA, Gehring AM, Stipanuk MH. Identification and characterization of bacterial cysteine dioxygenases: a new route of cysteine degradation for eubacteria. J Bacteriol 2006; 188:5561-9. [PMID: 16855246 PMCID: PMC1540046 DOI: 10.1128/jb.00291-06] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In metazoa and fungi, the catabolic dissimilation of cysteine begins with its sulfoxidation to cysteine sulfinic acid by the enzyme cysteine dioxygenase (CDO). In these organisms, CDO plays an important role in the homeostatic regulation of steady-state cysteine levels and provides important oxidized metabolites of cysteine such as sulfate and taurine. To date, there has been no experimental evidence for the presence of CDO in prokaryotes. Using PSI-BLAST searches and crystallographic information about the active-site geometry of mammalian CDOs, we identified a total of four proteins from Bacillus subtilis, Bacillus cereus, and Streptomyces coelicolor A3(2) that shared low overall identity to CDO (13 to 21%) but nevertheless conserved important active-site residues. These four proteins were heterologously expressed and purified to homogeneity by a single-step immobilized metal affinity chromatography procedure. The ability of these proteins to oxidize cysteine to cysteine sulfinic acid was then compared against recombinant rat CDO. The kinetic data strongly indicate that these proteins are indeed bona fide CDOs. Phylogenetic analyses of putative bacterial CDO homologs also indicate that CDO is distributed among species within the phyla of Actinobacteria, Firmicutes, and Proteobacteria. Collectively, these data suggest that a large subset of eubacteria is capable of cysteine sulfoxidation. Suggestions are made for how this novel pathway of cysteine metabolism may play a role in the life cycle of the eubacteria that have it.
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Affiliation(s)
- John E Dominy
- Division of Nutritional Sciences, 227 Savage Hall, Cornell University, Ithaca, NY 14853, USA
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Simmons CR, Liu Q, Huang Q, Hao Q, Begley TP, Karplus PA, Stipanuk MH. Crystal Structure of Mammalian Cysteine Dioxygenase. J Biol Chem 2006; 281:18723-33. [PMID: 16611640 DOI: 10.1074/jbc.m601555200] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine dioxygenase is a mononuclear iron-dependent enzyme responsible for the oxidation of cysteine with molecular oxygen to form cysteine sulfinate. This reaction commits cysteine to either catabolism to sulfate and pyruvate or the taurine biosynthetic pathway. Cysteine dioxygenase is a member of the cupin superfamily of proteins. The crystal structure of recombinant rat cysteine dioxygenase has been determined to 1.5-A resolution, and these results confirm the canonical cupin beta-sandwich fold and the rare cysteinyltyrosine intramolecular cross-link (between Cys(93) and Tyr(157)) seen in the recently reported murine cysteine dioxygenase structure. In contrast to the catalytically inactive mononuclear Ni(II) metallocenter present in the murine structure, crystallization of a catalytically competent preparation of rat cysteine dioxygenase revealed a novel tetrahedrally coordinated mononuclear iron center involving three histidines (His(86), His(88), and His(140)) and a water molecule. Attempts to acquire a structure with bound ligand using either cocrystallization or soaking crystals with cysteine revealed the formation of a mixed disulfide involving Cys(164) near the active site, which may explain previously observed substrate inhibition. This work provides a framework for understanding the molecular mechanisms involved in thiol dioxygenation and sets the stage for exploration of the chemistry of both the novel mononuclear iron center and the catalytic role of the cysteinyl-tyrosine linkage.
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Affiliation(s)
- Chad R Simmons
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853-8001, USA
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Stipanuk MH, Dominy JE, Lee JI, Coloso RM. Mammalian cysteine metabolism: new insights into regulation of cysteine metabolism. J Nutr 2006; 136:1652S-1659S. [PMID: 16702335 DOI: 10.1093/jn/136.6.1652s] [Citation(s) in RCA: 356] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mammalian liver tightly regulates its free cysteine pool, and intracellular cysteine in rat liver is maintained between 20 and 100 nmol/g even when sulfur amino acid intakes are deficient or excessive. By keeping cysteine levels within a narrow range and by regulating the synthesis of glutathione, which serves as a reservoir of cysteine, the liver addresses both the need to have adequate cysteine to support normal metabolism and the need to keep cysteine levels below the threshold of toxicity. Cysteine catabolism is tightly regulated via regulation of cysteine dioxygenase (CDO) levels in the liver, with the turnover of CDO protein being dramatically decreased when intracellular cysteine levels increase. This occurs in response to changes in the intracellular cysteine concentration via changes in the rate of CDO ubiquitination and degradation. Glutathione synthesis also increases when intracellular cysteine levels increase as a result of increased saturation of glutamate-cysteine ligase (GCL) with cysteine, and this contributes to removal of excess cysteine. When cysteine levels drop, GCL activity increases, and the increased capacity for glutathione synthesis facilitates conservation of cysteine in the form of glutathione (although the absolute rate of glutathione synthesis still decreases because of the lack of substrate). This increase in GCL activity is dependent on up-regulation of expression of both the catalytic and modifier subunits of GCL, resulting in an increase in total catalytic subunit plus an increase in the catalytic efficiency of the enzyme. An important role of cysteine utilization for coenzyme A synthesis in maintaining cellular cysteine levels in some tissues, and a possible connection between the necessity of controlling cellular cysteine levels to regulate the rate of hydrogen sulfide production, have been suggested by recent literature and are areas that deserve further study.
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Affiliation(s)
- Martha H Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA.
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