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Kong L, Dong Y, Shu G, Feng Y, Zhu M. Multienzyme-Mediated Dual-Channel Magnetic Relaxation Switching Taste Biosensor (D-MRSTB) for Simultaneous Detection of Umami Compounds and Synergistic Enhancement in Food. ACS Sens 2024; 9:1820-1830. [PMID: 38604805 DOI: 10.1021/acssensors.3c02366] [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] [Indexed: 04/13/2024]
Abstract
Umami substances play a significant role in the evaluation of food quality, and their synergistic enhancement is of great importance in improving and intensifying food flavors and tastes. Current biosensors available for umami detection still confront challenges in simultaneous quantification of multiple umami substances and umami intensities. In this study, an innovative dual-channel magnetic relaxation switching taste biosensor (D-MRSTB) was developed for the quantitative detection of representative umami substances. The multienzyme signal of D-MRSTB specifically catalyzes the umami substances of interest to generate hydrogen peroxide (H2O2), which is then used to oxidate Fe2+ to Fe3+. Such a valence-state transition of paramagnetic ions was utilized as a magnetic relaxation signaling switch to influence the transverse magnetic relaxation time (T2) within the reaction milieu, thus achieving simultaneous detection of monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP). The biosensor showed good linearity (R2 > 0.99) in the concentration range of 50-1000 and 10-1000 μmol/L, with limits of detection (LOD) of 0.61 and 0.09 μmol/L for MSG and IMP, respectively. Furthermore, the biosensor accurately characterized the synergistic effect of the mixed solution of IMP and MSG, where ΔT2 showed a good linear relationship with the equivalent umami concentration (EUC) of the mixed solution (R2 = 0.998). Moreover, the D-MRSTB successfully achieved the quantitative detection of umami compounds in real samples. This sensing technology provides a powerful tool for achieving the detection of synergistic enhancement among umami compounds and demonstrates its potential for application in the food industry.
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Affiliation(s)
- Liqin Kong
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, Hubei, China
| | - Yongzhen Dong
- Academy of Food Interdisciplinary Science, School of Food Science and Technology, Dalian Polytechnic University, Ganjingzi District, Dalian 116039, China
- State Key Laboratory of Marine Food Processing and Safety Control, Dalian Polytechnic University, Dalian 116039, Liaoning, China
| | - Guoqiang Shu
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, Hubei, China
| | - Yaoze Feng
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, Hubei, China
- Key Laboratory of Aquaculture Facilities Engineering, Ministry of Agriculture and Rural Affairs, Wuhan 430070, Hubei, China
- Interdisciplinary Sciences Research Institute, Huazhong Agricultural University, Wuhan 430070, Hubei, China
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518000, China
| | - Ming Zhu
- College of Engineering, Huazhong Agricultural University, Wuhan 430070, Hubei, China
- Key Laboratory of Aquaculture Facilities Engineering, Ministry of Agriculture and Rural Affairs, Wuhan 430070, Hubei, China
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Maghsoud Y, Dong C, Cisneros GA. Investigation of the Inhibition Mechanism of Xanthine Oxidoreductase by Oxipurinol: A Computational Study. J Chem Inf Model 2023. [PMID: 37319436 PMCID: PMC10405278 DOI: 10.1021/acs.jcim.3c00624] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Xanthine oxidoreductase (XOR) is an enzyme found in various organisms. It converts hypoxanthine to xanthine and urate, which are crucial steps in purine elimination in humans. Elevated uric acid levels can lead to conditions like gout and hyperuricemia. Therefore, there is significant interest in developing drugs that target XOR for treating these conditions and other diseases. Oxipurinol, an analogue of xanthine, is a well-known inhibitor of XOR. Crystallographic studies have revealed that oxipurinol directly binds to the molybdenum cofactor (MoCo) in XOR. However, the precise details of the inhibition mechanism are still unclear, which would be valuable for designing more effective drugs with similar inhibitory functions. In this study, molecular dynamics and quantum mechanics/molecular mechanics calculations are employed to investigate the inhibition mechanism of XOR by oxipurinol. The study examines the structural and dynamic effects of oxipurinol on the pre-catalytic structure of the metabolite-bound system. Our results provide insights on the reaction mechanism catalyzed by the MoCo center in the active site, which aligns well with experimental findings. Furthermore, the results provide insights into the residues surrounding the active site and propose an alternative mechanism for developing alternative covalent inhibitors.
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Affiliation(s)
- Yazdan Maghsoud
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Chao Dong
- Department of Chemistry and Physics, The University of Texas Permian Basin, Odessa, Texas 79762, United States
| | - G Andrés Cisneros
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, United States
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3
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Maghsoud Y, Dong C, Cisneros GA. Computational Characterization of the Inhibition Mechanism of Xanthine Oxidoreductase by Topiroxostat. ACS Catal 2023; 13:6023-6043. [PMID: 37547543 PMCID: PMC10399974 DOI: 10.1021/acscatal.3c01245] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Xanthine oxidase (XO) is a member of the molybdopterin-containing enzyme family. It interconverts xanthine to uric acid as the last step of purine catabolism in the human body. The high uric acid concentration in the blood directly leads to human diseases like gout and hyperuricemia. Therefore, drugs that inhibit the biosynthesis of uric acid by human XO have been clinically used for many years to decrease the concentration of uric acid in the blood. In this study, the inhibition mechanism of XO and a new promising drug, topiroxostat (code: FYX-051), is investigated by employing molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) calculations. This drug has been reported to act as both a noncovalent and covalent inhibitor and undergoes a stepwise inhibition by all its hydroxylated metabolites, which include 2-hydroxy-FYX-051, dihydroxy-FYX-051, and trihydroxy-FYX-051. However, the detailed mechanism of inhibition of each metabolite remains elusive and can be useful for designing more effective drugs with similar inhibition functions. Hence, herein we present the computational investigation of the structural and dynamical effects of FYX-051 and the calculated reaction mechanism for all of the oxidation steps catalyzed by the molybdopterin center in the active site. Calculated results for the proposed reaction mechanisms for each metabolite's inhibition reaction in the enzyme's active site, binding affinities, and the noncovalent interactions with the surrounding amino acid residues are consistent with previously reported experimental findings. Analysis of the noncovalent interactions via energy decomposition analysis (EDA) and noncovalent interaction (NCI) techniques suggests that residues L648, K771, E802, R839, L873, R880, R912, F914, F1009, L1014, and A1079 can be used as key interacting residues for further hybrid-type inhibitor development.
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Affiliation(s)
- Yazdan Maghsoud
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Chao Dong
- Department of Chemistry and Physics, The University of Texas Permian Basin, Odessa, Texas 79762, United States
| | - G Andrés Cisneros
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States; Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, United States
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4
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Gates C, Varnum H, Getty C, Loui N, Chen J, Kirk ML, Yang J, Nieter Burgmayer SJ. Protonation and Non-Innocent Ligand Behavior in Pyranopterin Dithiolene Molybdenum Complexes. Inorg Chem 2022; 61:13728-13742. [PMID: 36000991 PMCID: PMC10544801 DOI: 10.1021/acs.inorgchem.2c01234] [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: 11/28/2022]
Abstract
The complex [TEA][Tp*MoIV(O)(S2BMOPP)] (1) [TEA = tetraethylammonium, Tp* = tris(3,5-dimethylpyrazolyl)hydroborate, and BMOPP = 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl pterin] is a structural analogue of the molybdenum cofactor common to all pyranopterin molybdenum enzymes because it possesses a pyranopterin-ene-1,2-dithiolate ligand (S2BMOPP) that exists primarily in the ring-closed pyrano structure as a resonance hybrid of ene-dithiolate and thione-thiolate forms. Compound 1, the protonated [Tp*MoIV(O)(S2BMOPP-H)] (1-H) and one-electron-oxidized [Tp*MoV(O)(S2BMOPP)] [1-Mo(5+)] species have been studied using a combination of electrochemistry, electronic absorption, and electron paramagnetic resonance (EPR) spectroscopy. Additional insight into the nature of these molecules has been derived from electronic structure computations. Differences in dithiolene C-S bond lengths correlate with relative contributions from both ene-dithiolate and thione-thiolate resonance structures. Upon protonation of 1 to form 1-H, large spectroscopic changes are observed with transitions assigned as Mo(xy) → pyranopterin metal-to-ligand charge transfer and dithiolene → pyranopterin intraligand charge transfer, respectively, and this underscores a dramatic change in electronic structure between 1 and 1-H. The changes in electronic structure that occur upon protonation of 1 are also reflected in a large >300 mV increase in the Mo(V/IV) redox potential for 1-H, resulting from the greater thione-thiolate resonance contribution and decreased charge donation that stabilize the Mo(IV) state in 1-H with respect to one-electron oxidation. EPR spin Hamiltonian parameters for one-electron-oxidized 1-Mo(5+) and uncyclized [Tp*MoV(O)(S2BDMPP)] [3-Mo(5+)] [BDMPP = 6-(3-butynyl-2,2-dimethyl)-2-pivaloyl pterin] are very similar to each other and to those of [Tp*MoVO(bdt)] (bdt = 1,2-ene-dithiolate). This indicates that the dithiolate form of the ligand dominates at the Mo(V) level, consistent with the demand for greater S → Mo charge donation and a corresponding increase in Mo-S covalency as the oxidation state of the metal is increased. Protonation of 1 represents a simple reaction that models how the transfer of a proton from neighboring acidic amino acid residues to the Mo cofactor at a nitrogen atom within the pyranopterin dithiolene (PDT) ligand in pyranopterin molybdenum enzymes can impact the electronic structure of the Mo-PDT unit. This work also illustrates how pyran ring-chain tautomerization drives changes in resonance contributions to the dithiolene chelate and may adjust the reduction potential of the Mo ion.
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Affiliation(s)
- Cassandra Gates
- Department of Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, United States
| | - Haley Varnum
- Department of Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, United States
| | - Catherine Getty
- Department of Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, United States
| | - Natalie Loui
- Department of Chemistry, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, United States
| | - Ju Chen
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Jing Yang
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
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5
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Computational exploration of reactive fragment for mechanism-based inhibition of xanthine oxidase. J Organomet Chem 2018. [DOI: 10.1016/j.jorganchem.2018.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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6
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Saswati, Roy S, Dash SP, Acharyya R, Kaminsky W, Ugone V, Garribba E, Harris C, Lowe JM, Dinda R. Chemistry of oxidomolybdenum(IV) and -(VI) complexes with ONS donor ligands: Synthesis, computational evaluation and oxo-transfer reactions. Polyhedron 2018. [DOI: 10.1016/j.poly.2017.12.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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7
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Yang J, Dong C, Kirk ML. Xanthine oxidase-product complexes probe the importance of substrate/product orientation along the reaction coordinate. Dalton Trans 2017; 46:13242-13250. [PMID: 28696463 PMCID: PMC5634921 DOI: 10.1039/c7dt01728f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A combination of reaction coordinate computations, resonance Raman spectroscopy, spectroscopic computations, and hydrogen bonding investigations have been used to understand the importance of substrate orientation along the xanthine oxidase reaction coordinate. Specifically, 4-thiolumazine and 2,4-dithiolumazine have been used as reducing substrates for xanthine oxidase to form stable enzyme-product charge transfer complexes suitable for spectroscopic study. Laser excitation into the near-infrared molybdenum-to-product charge transfer band produces rR enhancement patterns in the high frequency in-plane stretching region that directly probe the nature of this MLCT transition and provide insight into the effects of electron redistribution along the reaction coordinate between the transition state and the stable enzyme-product intermediate, including the role of the covalent Mo-O-C linkage in facilitating this process. The results clearly show that specific Mo-substrate orientations allow for enhanced electronic coupling and facilitate strong hydrogen bonding interactions with amino acid residues in the substrate binding pocket.
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Affiliation(s)
- Jing Yang
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM87131-0001, USA.
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8
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Kumar R, Joshi G, Kler H, Kalra S, Kaur M, Arya R. Toward an Understanding of Structural Insights of Xanthine and Aldehyde Oxidases: An Overview of their Inhibitors and Role in Various Diseases. Med Res Rev 2017; 38:1073-1125. [DOI: 10.1002/med.21457] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 06/05/2017] [Accepted: 06/13/2017] [Indexed: 12/23/2022]
Affiliation(s)
- Raj Kumar
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
| | - Gaurav Joshi
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
| | - Harveen Kler
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
| | - Sourav Kalra
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
- Centre for Human Genetics and Molecular Medicine
| | - Manpreet Kaur
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
| | - Ramandeep Arya
- Laboratory for Drug Design and Synthesis, Centre for Pharmaceutical Sciences and Natural Products, School of Basic and Applied Sciences; Central University of Punjab; Bathinda 151001 India
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9
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Xanthine oxidase inhibitors beyond allopurinol and febuxostat; an overview and selection of potential leads based on in silico calculated physico-chemical properties, predicted pharmacokinetics and toxicity. Eur J Med Chem 2017; 135:491-516. [PMID: 28478180 DOI: 10.1016/j.ejmech.2017.04.031] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/28/2017] [Accepted: 04/12/2017] [Indexed: 02/06/2023]
Abstract
Xanthine oxidase (XO), a versatile metalloflavoprotein enzyme, catalyzes the oxidative hydroxylation of hypoxanthine and xanthine to uric acid in purine catabolism while simultaneously producing reactive oxygen species. Both lead to the gout-causing hyperuricemia and oxidative damage of the tissues where overactivity of XO is present. Over the past years, significant progress and efforts towards the discovery and development of new XO inhibitors have been made and we believe that not only experts in the field, but also general readership would benefit from a review that addresses this topic. Accordingly, the aim of this article was to overview and select the most potent recently reported XO inhibitors and to compare their structures, mechanisms of action, potency and effectiveness of their inhibitory activity, in silico calculated physico-chemical properties as well as predicted pharmacokinetics and toxicity. Derivatives of imidazole, 1,3-thiazole and pyrimidine proved to be more potent than febuxostat while also displaying/possessing favorable predicted physico-chemical, pharmacokinetic and toxicological properties. Although being structurally similar to febuxostat, these optimized inhibitors bear some structural freshness and could be adopted as hits for hit-to-lead development and further evaluation by in vivo studies towards novel drug candidates, and represent valuable model structures for design of novel XO inhibitors.
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10
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Seenivasan R, Kolodziej C, Karunakaran C, Burda C. Nanotechnology for Electroanalytical Biosensors of Reactive Oxygen and Nitrogen Species. CHEM REC 2017; 17:886-901. [DOI: 10.1002/tcr.201600143] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Indexed: 01/02/2023]
Affiliation(s)
- Rajesh Seenivasan
- Department of Chemistry; Case Western Reserve University; 10900 Euclid Ave. Cleveland OH 44106 USA
- Department of Electrical and Computer Engineering; University of California San Diego; 9500 Gilman Drive La Jolla CA 92093 USA
| | - Charles Kolodziej
- Department of Chemistry; Case Western Reserve University; 10900 Euclid Ave. Cleveland OH 44106 USA
| | - Chandran Karunakaran
- Department of Chemistry, Biomedical Research Lab; VHNSN College (Autonomous); 3/151-1,College Road, Virudhunagar Tamil Nadu 626001 India
| | - Clemens Burda
- Department of Chemistry; Case Western Reserve University; 10900 Euclid Ave. Cleveland OH 44106 USA
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11
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Priftis A, Papikinos K, Koukoulanaki M, Kerasioti E, Stagos D, Konstantinopoulos K, Spandidos DA, Kermenidou M, Karakitsios S, Sarigiannis D, Tsatsakis AM, Kouretas D. Development of an assay to assess genotoxicity by particulate matter extract. Mol Med Rep 2017; 15:1738-1746. [PMID: 28260086 PMCID: PMC5365018 DOI: 10.3892/mmr.2017.6171] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/30/2017] [Indexed: 01/11/2023] Open
Abstract
The current study describes a method for assessing the oxidative potential of common environmental stressors (ambient air particulate matter), using a plasmid relaxation assay where the extract caused single-strand breaks, easily visualised through electrophoresis. This assay utilises a miniscule amount (11 µg) of particulate matter (PM) extract compared to other, cell-based methods (~3,000 µg). The negative impact of air pollution on human health has been extensively recognised. Among the air pollutants, PM plays an eminent role, as reflected in the broad scientific interest. PM toxicity highly depends on its composition (metals and organic compounds), which in turn has been linked to multiple health effects (such as cardiorespiratory diseases and cancer) through multiple toxicity mechanisms; the induction of oxidative stress is considered a major mechanism among these. In this study, the PM levels, oxidative potential, cytotoxicity and genotoxicity of PM in the region of Larissa, Greece were examined using the plasmid relaxation assay. Finally, coffee extracts from different varieties, derived from both green and roasted seeds, were examined for their ability to inhibit PM-induced DNA damage. These extracts also exerted an inhibitory effect on xanthine oxidase and catalase, but had no effect against superoxide dismutase. Overall, this study highlights the importance of assays for assessing the oxidative potential of widespread environmental stressors (PM), as well as the antioxidant capacity of beverages and food items, with the highlight being the development of a plasmid relaxation assay to assess the genotoxicity caused by PM using only a miniscule amount.
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Affiliation(s)
- Alexandros Priftis
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
| | - Konstantinos Papikinos
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
| | - Marina Koukoulanaki
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
| | - Efthalia Kerasioti
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
| | - Dimitrios Stagos
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
| | | | - Demetrios A Spandidos
- Laboratory of Clinical Virology, University of Crete, Medical School, Heraklion 71409, Greece
| | - Marianthi Kermenidou
- Aristotle University of Thessaloniki, Department of Chemical Engineering, Environmental Engineering Laboratory, Thessaloniki 54124, Greece
| | - Spyros Karakitsios
- Aristotle University of Thessaloniki, Department of Chemical Engineering, Environmental Engineering Laboratory, Thessaloniki 54124, Greece
| | - Dimosthenis Sarigiannis
- Aristotle University of Thessaloniki, Department of Chemical Engineering, Environmental Engineering Laboratory, Thessaloniki 54124, Greece
| | - Aristides M Tsatsakis
- Department of Forensic Sciences and Toxicology, Medical School, University of Crete, Heraklion 71003, Greece
| | - Demetrios Kouretas
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa 41221, Greece
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12
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Mirzaei S, Taherpour AA, Mohamadi S. Mechanistic study of allopurinol oxidation using aldehyde oxidase, xanthine oxidase and cytochrome P450 enzymes. RSC Adv 2016. [DOI: 10.1039/c6ra19197e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The oxidation reaction of allopurinol to its active metabolite (oxypurinol) is investigated using the AO and P450 enzymes. To the contrary of AO (and XO), the P450 enzyme can metabolize the allopurinol with a not self-inhibitory mechanism.
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Affiliation(s)
- Saber Mirzaei
- Department of Organic Chemistry
- Faculty of Chemistry
- Razi University
- Kermanshah
- Iran
| | - Avat Arman Taherpour
- Department of Organic Chemistry
- Faculty of Chemistry
- Razi University
- Kermanshah
- Iran
| | - Shahryar Mohamadi
- Department of Organic Chemistry
- Faculty of Chemistry
- Razi University
- Kermanshah
- Iran
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13
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Stein BW, Kirk ML. Electronic structure contributions to reactivity in xanthine oxidase family enzymes. J Biol Inorg Chem 2015; 20:183-94. [PMID: 25425163 PMCID: PMC4867223 DOI: 10.1007/s00775-014-1212-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 10/30/2014] [Indexed: 11/25/2022]
Abstract
We review the xanthine oxidase (XO) family of pyranopterin molybdenum enzymes with a specific emphasis on electronic structure contributions to reactivity. In addition to xanthine and aldehyde oxidoreductases, which catalyze the two-electron oxidation of aromatic heterocycles and aldehyde substrates, this mini-review highlights recent work on the closely related carbon monoxide dehydrogenase (CODH) that catalyzes the oxidation of CO using a unique Mo-Cu heterobimetallic active site. A primary focus of this mini-review relates to how spectroscopy and computational methods have been used to develop an understanding of critical relationships between geometric structure, electronic structure, and catalytic function.
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Affiliation(s)
- Benjamin W. Stein
- Department of Chemistry and Chemical Biology, University of New Mexico, MSC03 2060, 300 Terrace St. NE, Albuquerque, NM 87131
| | - Martin L. Kirk
- Department of Chemistry and Chemical Biology, University of New Mexico, MSC03 2060, 300 Terrace St. NE, Albuquerque, NM 87131
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14
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Hall J, Reschke S, Cao H, Leimkühler S, Hille R. The reductive half-reaction of xanthine dehydrogenase from Rhodobacter capsulatus: the role of Glu232 in catalysis. J Biol Chem 2014; 289:32121-32130. [PMID: 25258317 DOI: 10.1074/jbc.m114.603456] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The kinetic properties of an E232Q variant of the xanthine dehydrogenase from Rhodobacter capsulatus have been examined to ascertain whether Glu(232) in wild-type enzyme is protonated or unprotonated in the course of catalysis at neutral pH. We find that kred, the limiting rate constant for reduction at high [xanthine], is significantly compromised in the variant, a result that is inconsistent with Glu(232) being neutral in the active site of the wild-type enzyme. A comparison of the pH dependence of both kred and kred/Kd from reductive half-reaction experiments between wild-type and enzyme and the E232Q variant suggests that the ionized Glu(232) of wild-type enzyme plays an important role in catalysis by discriminating against the monoanionic form of substrate, effectively increasing the pKa of substrate by two pH units and ensuring that at physiological pH the neutral form of substrate predominates in the Michaelis complex. A kinetic isotope study of the wild-type R. capsulatus enzyme indicates that, as previously determined for the bovine and chicken enzymes, product release is principally rate-limiting in catalysis. The disparity in rate constants for the chemical step of the reaction and product release, however, is not as great in the bacterial enzyme as compared with the vertebrate forms. The results indicate that the bacterial and bovine enzymes catalyze the chemical step of the reaction to the same degree and that the faster turnover observed with the bacterial enzyme is due to a faster rate constant for product release than is seen with the vertebrate enzyme.
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Affiliation(s)
- James Hall
- Department of Biochemistry, University of California, Riverside, California 92521 and
| | - Stefan Reschke
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University Potsdam, 14476 Potsdam, Germany
| | - Hongnan Cao
- Department of Biochemistry, University of California, Riverside, California 92521 and
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University Potsdam, 14476 Potsdam, Germany
| | - Russ Hille
- Department of Biochemistry, University of California, Riverside, California 92521 and.
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15
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Sparacino-Watkins C, Stolz JF, Basu P. Nitrate and periplasmic nitrate reductases. Chem Soc Rev 2014; 43:676-706. [PMID: 24141308 DOI: 10.1039/c3cs60249d] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types--periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed.
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Kalimuthu P, Leimkühler S, Bernhardt PV. Catalytic Electrochemistry of Xanthine Dehydrogenase. J Phys Chem B 2012; 116:11600-7. [DOI: 10.1021/jp307374z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Palraj Kalimuthu
- School of Chemistry and Molecular
Biosciences, University of Queensland,
Brisbane 4072, Australia
| | - Silke Leimkühler
- Institut für Biochemie
und Biologie, Universität Potsdam, 14476 Potsdam, Germany
| | - Paul V. Bernhardt
- School of Chemistry and Molecular
Biosciences, University of Queensland,
Brisbane 4072, Australia
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Charged dioxomolybdenum(VI) complexes with pyridoxal thiosemicarbazone ligands as molybdenum(V) precursors in oxygen atom transfer process and epoxidation (pre)catalysts. Polyhedron 2012. [DOI: 10.1016/j.poly.2011.12.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Plank MS, Calderon TC, Asmerom Y, Boskovic DS, Angeles DM. Biochemical measurement of neonatal hypoxia. J Vis Exp 2011:2948. [PMID: 21897351 DOI: 10.3791/2948] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Neonatal hypoxia ischemia is characterized by inadequate blood perfusion of a tissue or a systemic lack of oxygen. This condition is thought to cause/exacerbate well documented neonatal disorders including neurological impairment. Decreased adenosine triphosphate production occurs due to a lack of oxidative phosphorylation. To compensate for this energy deprived state molecules containing high energy phosphate bonds are degraded. This leads to increased levels of adenosine which is subsequently degraded to inosine, hypoxanthine, xanthine, and finally to uric acid. The final two steps in this degradation process are performed by xanthine oxidoreductase. This enzyme exists in the form of xanthine dehydrogenase under normoxic conditions but is converted to xanthine oxidase (XO) under hypoxia-reperfusion circumstances. Unlike xanthine dehydrogenase, XO generates hydrogen peroxide as a byproduct of purine degradation. This hydrogen peroxide in combination with other reactive oxygen species (ROS) produced during hypoxia, oxidizes uric acid to form allantoin and reacts with lipid membranes to generate malondialdehyde (MDA). Most mammals, humans exempted, possess the enzyme uricase, which converts uric acid to allantoin. In humans, however, allantoin can only be formed by ROS-mediated oxidation of uric acid. Because of this, allantoin is considered to be a marker of oxidative stress in humans, but not in the mammals that have uricase. We describe methods employing high pressure liquid chromatography (HPLC) and gas chromatography mass spectrometry (GCMS) to measure biochemical markers of neonatal hypoxia ischemia. Human blood is used for most tests. Animal blood may also be used while recognizing the potential for uricase-generated allantoin. Purine metabolites were linked to hypoxia as early as 1963 and the reliability of hypoxanthine, xanthine, and uric acid as biochemical indicators of neonatal hypoxia was validated by several investigators. The HPLC method used for the quantification of purine compounds is fast, reliable, and reproducible. The GC/MS method used for the quantification of allantoin, a relatively new marker of oxidative stress, was adapted from Gruber et al. This method avoids certain artifacts and requires low volumes of sample. Methods used for synthesis of MMDA were described elsewhere. GC/MS based quantification of MDA was adapted from Paroni et al. and Cighetti et al. Xanthine oxidase activity was measured by HPLC by quantifying the conversion of pterin to isoxanthopterin. This approach proved to be sufficiently sensitive and reproducible.
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Affiliation(s)
- Megan S Plank
- Division of Biochemistry, Department of Basic Sciences, Loma Linda University, USA
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20
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Kalimuthu P, Leimkühler S, Bernhardt PV. Xanthine dehydrogenase electrocatalysis: autocatalysis and novel activity. J Phys Chem B 2011; 115:2655-62. [PMID: 21361328 DOI: 10.1021/jp111809f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The enzyme xanthine dehydrogenase (XDH) from the purple photosynthetic bacterium Rhodobacter capsulatus catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid as part of purine metabolism. The native electron acceptor is NAD(+) but herein we show that uric acid in its 2-electron oxidized form is able to act as an artificial electron acceptor from XDH in an electrochemically driven catalytic system. Hypoxanthine oxidation is also observed with the novel production of uric acid in a series of two consecutive 2-electron oxidation reactions via xanthine. XDH exhibits native activity in terms of its pH optimum and inhibition by allopurinol.
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Affiliation(s)
- Palraj Kalimuthu
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland , Brisbane, 4072, Australia and
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21
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Urate Is a Ligand for the Transcriptional Regulator PecS. J Mol Biol 2010; 402:539-51. [DOI: 10.1016/j.jmb.2010.07.053] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 07/17/2010] [Accepted: 07/26/2010] [Indexed: 11/22/2022]
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22
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Active transition metal oxo and hydroxo moieties in nature's redox, enzymes and their synthetic models: Structure and reactivity relationships. Coord Chem Rev 2010. [DOI: 10.1016/j.ccr.2010.01.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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23
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Dieterich JM, Werner HJ, Mata RA, Metz S, Thiel W. Reductive half-reaction of aldehyde oxidoreductase toward acetaldehyde: Ab initio and free energy quantum mechanical/molecular mechanical calculations. J Chem Phys 2010; 132:035101. [DOI: 10.1063/1.3280164] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Metz S, Thiel W. QM/MM Studies of Xanthine Oxidase: Variations of Cofactor, Substrate, and Active-Site Glu802. J Phys Chem B 2010; 114:1506-17. [DOI: 10.1021/jp909999s] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sebastian Metz
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
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25
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Gibson EA, Duhme-Klair AK, Perutz RN. Design and synthesis of water soluble (metallo)porphyrins with pendant arms: studies of binding to xanthine oxidase. NEW J CHEM 2010. [DOI: 10.1039/b9nj00736a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Theoretical study of three predominant tautomers of 2-oxo-6-methylpurine and their two transition state structures. Tetrahedron Lett 2010. [DOI: 10.1016/j.tetlet.2009.11.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Metz S, Thiel W. A Combined QM/MM Study on the Reductive Half-Reaction of Xanthine Oxidase: Substrate Orientation and Mechanism. J Am Chem Soc 2009; 131:14885-902. [DOI: 10.1021/ja9045394] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Sebastian Metz
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
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28
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Bayse CA. Density-functional theory models of xanthine oxidoreductase activity: comparison of substrate tautomerization and protonation. Dalton Trans 2009:2306-14. [DOI: 10.1039/b821878a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Schumann S, Saggu M, Möller N, Anker SD, Lendzian F, Hildebrandt P, Leimkühler S. The mechanism of assembly and cofactor insertion into Rhodobacter capsulatus xanthine dehydrogenase. J Biol Chem 2008; 283:16602-11. [PMID: 18390908 DOI: 10.1074/jbc.m709894200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodobacter capsulatus xanthine dehydrogenase (XDH) is a molybdo-flavoprotein that is highly homologous to the homodimeric mammalian xanthine oxidoreductase. However, the bacterial enzyme has an (alphabeta)(2) heterotetrameric structure, and the cofactors were identified to be located on two different polypeptides. We have analyzed the mechanism of cofactor insertion and subunit assembly of R. capsulatus XDH, using engineered subunits with appropriate substitutions in the interfaces. In an (alphabeta) heterodimeric XDH containing the XdhA and XdhB subunits, the molybdenum cofactor (Moco) was shown to be absent, indicating that dimerization of the (alphabeta) subunits has to precede Moco insertion. In an (alphabeta)(2) XDH heterotetramer variant, including only one active Moco-center, the active (alphabeta) site of the chimeric enzyme was shown to be fully active, revealing that the two subunits act independent without cooperativity. Amino acid substitutions at two cysteine residues coordinating FeSI of the two [2Fe-2S] clusters of the enzyme demonstrate that an incomplete assembly of FeSI impairs the formation of the XDH (alphabeta)(2) heterotetramer and, thus, insertion of Moco into the enzyme. The results reveal that the insertion of the different redox centers into R. capsulatus XDH takes place sequentially. Dimerization of two (alphabeta) dimers is necessary for insertion of sulfurated Moco into apo-XDH, the last step of XDH maturation.
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Affiliation(s)
- Silvia Schumann
- Universität Potsdam, Institut für Biochemie and Biologie, Karl-Liebknecht Strasse 24-25, Potsdam 14476, Germany
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30
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Pauff JM, Zhang J, Bell CE, Hille R. Substrate orientation in xanthine oxidase: crystal structure of enzyme in reaction with 2-hydroxy-6-methylpurine. J Biol Chem 2007; 283:4818-24. [PMID: 18063585 DOI: 10.1074/jbc.m707918200] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Xanthine oxidoreductase catalyzes the final two steps of purine catabolism and is involved in a variety of pathological states ranging from hyperuricemia to ischemia-reperfusion injury. The human enzyme is expressed primarily in its dehydrogenase form utilizing NAD+ as the final electron acceptor from the enzyme's flavin site but can exist as an oxidase that utilizes O2 for this purpose. Central to an understanding of the enzyme's function is knowledge of purine substrate orientation in the enzyme's molybdenum-containing active site. We report here the crystal structure of xanthine oxidase, trapped at the stage of a critical intermediate in the course of reaction with the slow substrate 2-hydroxy-6-methylpurine at 2.3A. This is the first crystal structure of a reaction intermediate with a purine substrate that is hydroxylated at its C8 position as is xanthine and confirms the structure predicted to occur in the course of the presently favored reaction mechanism. The structure also corroborates recent work suggesting that 2-hydroxy-6-methylpurine orients in the active site with its C2 carbonyl group interacting with Arg-880 and extends our hypothesis that xanthine binds opposite this orientation, with its C6 carbonyl positioned to interact with Arg-880 in stabilizing the MoV transition state.
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Affiliation(s)
- James M Pauff
- Department of Biochemistry, University of California, Riverside, California 92521, USA
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31
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Berne C, Pignol D, Lavergne J, Garcia D. CYP201A2, a cytochrome P450 from Rhodopseudomonas palustris, plays a key role in the biodegradation of tributyl phosphate. Appl Microbiol Biotechnol 2007; 77:135-44. [PMID: 17786430 DOI: 10.1007/s00253-007-1140-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 07/26/2007] [Accepted: 07/31/2007] [Indexed: 10/22/2022]
Abstract
Tributyl phosphate (TBP) is a toxic organophosphorous compound widely used in nuclear fuel processing and chemical industries. Rhodopseudomonas palustris, one of the most metabolically versatile photosynthetic bacteria, is shown here to degrade TBP efficiently under photosynthetic conditions. This study shows that this O(2)- and NADPH/FMNH(2)-dependent process was also catalyzed when TBP was incubated with membrane-associated proteins extracted from this strain. The effects of several regulators of cytochrome P450 activity on the TBP consumption suggest a key role for a cytochrome P450 in this process. Disruption of the rpa0241 gene encoding a putative cytochrome P450 led to a 60% decrease of the TBP catabolism, whereas reintroducing the gene in the mutant restored the wild-type phenotype. The rpa0241 gene was expressed and purified in Escherichia coli. Characterization by UV-visible spectroscopy of the purified recombinant membrane-bound protein (CYP201A2) encoded by the rpa0241 gene revealed typical spectral characteristics of cytochrome P450 with a large spin state change of the heme iron associated with binding of TBP (K (d) approximately 65 microM). It is proposed that CYP201A2 catalyzes the initial step of the biodegradation process of TBP.
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Affiliation(s)
- Cécile Berne
- DSV/IBEB/SBVME/LBC, Unité Mixte de Recherche 6191, Centre National de la Recherche Scientifique/CEA/Univ. Aix-Marseille, CEA Cadarache, Saint Paul lez Durance, France
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32
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Bayse CA. Theoretical Characterization of the “Very Rapid” Mo(V) Species Generated in the Oxidation of Xanthine Oxidase. Inorg Chem 2006; 45:2199-202. [PMID: 16499383 DOI: 10.1021/ic0511930] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Density functional theory calculations of the "very rapid" Mo(V) intermediate of xanthine oxidase (XO) result in a square pyramidal geometry with end-on coordination of the model substrate. The Mo-C8 distance is 3.18 A, longer than previously reported from ENDOR experiments (<2.4 A Howes; et al. Biochemistry 1996, 35, 1432; 2.7-2.9 A Mandikandan; et al. J. Am. Chem. Soc. 2001, 123, 2658). Theoretical gas-phase isotropic hyperfine coupling constants A(iso)(C8) (B3LYP/BSII, 7.68 MHz; B3P86/BSII, 8.64 MHz) compare well with experimental values for the "very rapid" Mo(V) intermediate of XO with xanthine (8.8 MHz, Howes et al.) and 2-hydroxy-6-methylpurine (7.9 MHz, Mandikandan et al.). Absolute values of A(iso) of the metal-bound substrate oxygen are similar in magnitude to that of experiment.
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Affiliation(s)
- Craig A Bayse
- Department of Chemistry and Biochemistry, Old Dominion University, Hampton Boulevard, Norfolk, Virginia 23529, USA.
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Cultrone A, Scazzocchio C, Rochet M, Montero-Morán G, Drevet C, Fernández-Martín R. Convergent evolution of hydroxylation mechanisms in the fungal kingdom: molybdenum cofactor-independent hydroxylation of xanthine via α-ketoglutarate-dependent dioxygenases. Mol Microbiol 2005; 57:276-90. [PMID: 15948966 DOI: 10.1111/j.1365-2958.2005.04686.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The xanthine oxidases and dehydrogenases are among the most conserved enzymes in all living kingdoms. They contain the molybdopterin cofactor Moco. We show here that in the fungi, in addition to xanthine dehydrogenase, a completely different enzyme is able to catalyse the oxidation of xanthine to uric acid. In Aspergillus nidulans this enzyme is coded by the xanA gene. We have cloned the xanA gene and determined its sequence. A deletion of the gene has the same phenotype as the previously known xanA1 miss-sense mutation. Homologues of xanA exist only in the fungal kingdom. We have inactivated the cognate gene of Schizosaccharomyces pombe and this results in strongly impaired xanthine utilization as a nitrogen source. We have shown that the Neurospora crassa homologue is functionally equivalent to xanA. The enzyme coded by xanA is an alpha-ketoglutarate- and Fe(II)-dependent dioxygenase which shares a number of properties with other enzymes of this group. This work shows that only in the fungal kingdom, an alternative mechanism of xanthine oxidation, not involving Moco, has evolved using the dioxygenase scaffold.
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Affiliation(s)
- Antonietta Cultrone
- Institut de Génétique et de Microbiologie, Université Paris-Sud, Bâtiment 409, UMR 8621 CNRS, 91405 Orsay Cedex, France
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Affiliation(s)
- Feng Xu
- Novozymes, Inc., 1445 Drew Avenue, Davis, CA 95616, Phone: (530) 757-8138. Fax: (530) 757-4718., E-mail:
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