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Abstract
A survey of protein databases indicates that the majority of enzymes exist in oligomeric forms, with about half of those found in the UniProt database being homodimeric. Understanding why many enzymes are in their dimeric form is imperative. Recent developments in experimental and computational techniques have allowed for a deeper comprehension of the cooperative interactions between the subunits of dimeric enzymes. This review aims to succinctly summarize these recent advancements by providing an overview of experimental and theoretical methods, as well as an understanding of cooperativity in substrate binding and the molecular mechanisms of cooperative catalysis within homodimeric enzymes. Focus is set upon the beneficial effects of dimerization and cooperative catalysis. These advancements not only provide essential case studies and theoretical support for comprehending dimeric enzyme catalysis but also serve as a foundation for designing highly efficient catalysts, such as dimeric organic catalysts. Moreover, these developments have significant implications for drug design, as exemplified by Paxlovid, which was designed for the homodimeric main protease of SARS-CoV-2.
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Affiliation(s)
- Ke-Wei Chen
- Lab of Computional Chemistry and Drug Design, State Key Laboratory of Chemical Oncogenomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Tian-Yu Sun
- Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Yun-Dong Wu
- Lab of Computional Chemistry and Drug Design, State Key Laboratory of Chemical Oncogenomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
- Shenzhen Bay Laboratory, Shenzhen 518132, China
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Oozeki T, Nakai T, Kozakai K, Okamoto K, Kuroda S, Kobayashi K, Tanizawa K, Okajima T. Functional and structural characterization of a flavoprotein monooxygenase essential for biogenesis of tryptophylquinone cofactor. Nat Commun 2021; 12:933. [PMID: 33568660 PMCID: PMC7876137 DOI: 10.1038/s41467-021-21200-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 01/14/2021] [Indexed: 01/07/2023] Open
Abstract
Bioconversion of peptidyl amino acids into enzyme cofactors is an important post-translational modification. Here, we report a flavoprotein, essential for biosynthesis of a protein-derived quinone cofactor, cysteine tryptophylquinone, contained in a widely distributed bacterial enzyme, quinohemoprotein amine dehydrogenase. The purified flavoprotein catalyzes the single-turnover dihydroxylation of the tryptophylquinone-precursor, tryptophan, in the protein substrate containing triple intra-peptidyl crosslinks that are pre-formed by a radical S-adenosylmethionine enzyme within the ternary complex of these proteins. Crystal structure of the peptidyl tryptophan dihydroxylase reveals a large pocket that may dock the protein substrate with the bound flavin adenine dinucleotide situated close to the precursor tryptophan. Based on the enzyme-protein substrate docking model, we propose a chemical reaction mechanism of peptidyl tryptophan dihydroxylation catalyzed by the flavoprotein monooxygenase. The diversity of the tryptophylquinone-generating systems suggests convergent evolution of the peptidyl tryptophan-derived cofactors in different proteins.
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Affiliation(s)
- Toshinori Oozeki
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Tadashi Nakai
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan ,grid.417545.60000 0001 0665 883XFaculty of Life Sciences, Hiroshima Institute of Technology, Hiroshima, Japan
| | - Kazuki Kozakai
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Kazuki Okamoto
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Shun’ichi Kuroda
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Kazuo Kobayashi
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Katsuyuki Tanizawa
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Toshihide Okajima
- grid.136593.b0000 0004 0373 3971Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
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Mamounis KJ, Yukl ET, Davidson VL. Roles of active-site residues in catalysis, substrate binding, cooperativity, and the reaction mechanism of the quinoprotein glycine oxidase. J Biol Chem 2020; 295:6472-6481. [PMID: 32234764 DOI: 10.1074/jbc.ra120.013198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/30/2020] [Indexed: 11/06/2022] Open
Abstract
The quinoprotein glycine oxidase from the marine bacterium Pseudoalteromonas luteoviolacea (PlGoxA) uses a protein-derived cysteine tryptophylquinone (CTQ) cofactor to catalyze conversion of glycine to glyoxylate and ammonia. This homotetrameric enzyme exhibits strong cooperativity toward glycine binding. It is a good model for studying enzyme kinetics and cooperativity, specifically for being able to separate those aspects of protein function through directed mutagenesis. Variant proteins were generated with mutations in four active-site residues, Phe-316, His-583, Tyr-766, and His-767. Structures for glycine-soaked crystals were obtained for each. Different mutations had differential effects on k cat and K 0.5 for catalysis, K 0.5 for substrate binding, and the Hill coefficients describing the steady-state kinetics or substrate binding. Phe-316 and Tyr-766 variants retained catalytic activity, albeit with altered kinetics and cooperativity. Substitutions of His-583 revealed that it is essential for glycine binding, and the structure of H583C PlGoxA had no active-site glycine present in glycine-soaked crystals. The structure of H767A PlGoxA revealed a previously undetected reaction intermediate, a carbinolamine product-reduced CTQ adduct, and exhibited only negligible activity. The results of these experiments, as well as those with the native enzyme and previous variants, enabled construction of a detailed mechanism for the reductive half-reaction of glycine oxidation. This proposed mechanism includes three discrete reaction intermediates that are covalently bound to CTQ during the reaction, two of which have now been structurally characterized by X-ray crystallography.
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Affiliation(s)
- Kyle J Mamounis
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32827
| | - Erik T Yukl
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32827
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Fujieda N. His-Cys and Trp-Cys cross-links generated by post-translational chemical modification. Biosci Biotechnol Biochem 2019; 84:445-454. [PMID: 31771431 DOI: 10.1080/09168451.2019.1696178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Galactose oxidase and amine oxidase contain a cofactor which is generated by post-translational chemical modification to the corresponding amino acid side chains near the copper active center. Such cofactors provide proteins unusual catalytic ability that canonical amino acids cannot exert as well as their structural stability, and thereby are called as protein-derived cofactors. These cofactors and modifications are mostly derived from aromatic amino acid residues, especially Tyr, Trp, and His. Current information about unusual cofactors derived from two of those, heteroaromatic residues (Trp and His) is summarized, especially chemical properties and maturation process of the cross-links between cysteine and heteroaromatic amino acids (His-Cys and Trp-Cys cross-links).Abbreviations: FMN: flavin mononucleotide; FAD: flavin adenine nucleotide; RNA: ribonucleic acid; PDC: protein-derived cofactor; GFP: green fluorescent protein; MIO: 3,5-dihydro-5-methylidene-4-imidazol-4-one; LTQ: lysyl tyrosylquinone; CTQ: cysteine tryptophylquinone; TTQ: tryptophan tryptophylquinone; E.coli: Escherichia coli; WT: wild type.
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Affiliation(s)
- Nobutaka Fujieda
- Department of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan
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Mamounis KJ, Avalos D, Yukl ET, Davidson VL. Kinetic and structural evidence that Asp-678 plays multiple roles in catalysis by the quinoprotein glycine oxidase. J Biol Chem 2019; 294:17463-17470. [PMID: 31615898 DOI: 10.1074/jbc.ra119.011255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 10/10/2019] [Indexed: 11/06/2022] Open
Abstract
PlGoxA from Pseudoalteromonas luteoviolacea is a glycine oxidase that utilizes a protein-derived cysteine tryptophylquinone (CTQ) cofactor. A notable feature of its catalytic mechanism is that it forms a stable product-reduced CTQ adduct that is not hydrolyzed in the absence of O2 Asp-678 resides near the quinone moiety of PlGoxA, and an Asp is structurally conserved in this position in all tryptophylquinone enzymes. In those other enzymes, mutation of that Asp results in no or negligible CTQ formation. In this study, mutation of Asp-678 in PlGoxA did not abolish CTQ formation. This allowed, for the first time, studying the role of this residue in catalysis. D678A and D678N substitutions yielded enzyme variants with CTQ, which did not react with glycine, although glycine was present in the crystal structures in the active site. D678E PlGoxA was active but exhibited a much slower k cat This mutation altered the kinetic mechanism of the reductive half-reaction such that one could observe a previously undetected reactive intermediate, an initial substrate-oxidized CTQ adduct, which converted to the product-reduced CTQ adduct. These results indicate that Asp-678 is involved in the initial deprotonation of the amino group of glycine, enabling nucleophilic attack of CTQ, as well as the deprotonation of the substrate-oxidized CTQ adduct, which is coupled to CTQ reduction. The structures also suggest that Asp-678 is acting as a proton relay that directs these protons to a water channel that connects the active sites on the subunits of this homotetrameric enzyme.
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Affiliation(s)
- Kyle J Mamounis
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32827
| | - Dante Avalos
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003
| | - Erik T Yukl
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32827
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Following the Evolutionary Track of a Highly Specific l-Arginine Oxidase by Reconstruction and Biochemical Analysis of Ancestral and Native Enzymes. Appl Environ Microbiol 2019; 85:AEM.00459-19. [PMID: 30979835 DOI: 10.1128/aem.00459-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Accepted: 03/27/2019] [Indexed: 02/02/2023] Open
Abstract
Following the evolutionary track of enzymes can help elucidate how enzymes attain their characteristic functions, such as thermal adaptation and substrate selectivity, during the evolutionary process. Ancestral sequence reconstruction (ASR) is effective for following evolutionary processes if sufficient sequence data are available. Selecting sequences from the data to generate a curated sequence library is necessary for the successful design of artificial proteins by ASR. In this study, we tried to follow the evolutionary track of l-arginine oxidase (AROD), a flavin adenine dinucleotide (FAD)-dependent amino acid oxidase (LAAO) that exhibits high specificity for l-arginine. The library was generated by selecting sequences in which the 15th, 50th, 332nd, and 580th residues are Gly, Ser, Trp, and Thr, respectively. We excluded sequences that are either extremely short or long and those with a low degree of sequence identity. Three ancestral ARODs (AncARODn0, AncARODn1, and AncARODn2) were designed using the library. Subsequently, we expressed the ancestral ARODs as well as native Oceanobacter kriegii AROD (OkAROD) in bacteria. AncARODn0 is phylogenetically most remote from OkAROD, whereas AncARODn2 is most similar to OkAROD. Thermal stability was gradually increased by extending AROD sequences back to the progenitor, while the temperature at which the residual activity is half of the maximum measured activity (T 1/2) of AncARODn0 was >20°C higher than that of OkAROD. Remarkably, only AncARODn0 exhibited broad substrate selectivity similar to that of conventional promiscuous LAAO. Taken together, our findings led us to infer that AROD may have evolved from a highly thermostable and promiscuous LAAO.IMPORTANCE In this study, we attempted to infer the molecular evolution of a recently isolated FAD-dependent l-arginine oxidase (AROD) that oxidizes l-arginine to 2-ketoarginine. Utilizing 10 candidate AROD sequences, we obtained a total of three ancestral ARODs. In addition, one native AROD was obtained by cloning one of the candidate ARODs. The candidate sequences were selected utilizing a curation method defined in this study. All the ARODs were successfully expressed in Escherichia coli for analysis of their biochemical functions. The catalytic activity of our bacterially expressed ancestral ARODs suggests that our ASR was successful. The ancestral AROD that is phylogenetically most remote from a native AROD has the highest thermal stability and substrate promiscuity. Our findings led us to infer that AROD evolved from a highly thermostable and promiscuous LAAO. As an application, we can design artificial ARODs with improved functions compared with those of native ones.
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Ma Z, Davidson VL. The Redox Properties of a Cysteine Tryptophylquinone-Dependent Glycine Oxidase Are Distinct from Those of Tryptophylquinone-Dependent Dehydrogenases. Biochemistry 2019; 58:2243-2249. [PMID: 30945853 DOI: 10.1021/acs.biochem.9b00104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
GoxA is a cysteine tryptophylquinone (CTQ)-dependent glycine oxidase that is a member of a family of LodA-like proteins. The electrochemical midpoint potential ( Em) values for the quinone/semiquinone couple and the semiquinone/quinol couple were determined to be 111 and 21, respectively. The Em value for the overall two-electron quinone/quinol couple was similar to those of CTQ- and tryptophan tryptophylquinone (TTQ)-bearing dehydrogenases. However, for the well-studied TTQ-dependent methylamine dehydrogenase, the quinone/semiquinone couple is more negative than the semiquinone/quinol couple, the opposite of what was determined for GoxA. The change in Em value for the two-electron quinone/quinol couple of CTQ in GoxA with pH indicates that the overall two-electron transfer process is associated with the transfer of one proton. Thus, the quinol is anionic. The data reported herein further suggest that in GoxA the CTQ semiquinone is neutral, in contrast to the TTQ-dependent dehydrogenases, in which it is an anionic TTQ semiquinone. These results are discussed in the context of the structure and function of this glycine oxidase, compared to that of the tryptophylquinone-dependent dehydrogenases.
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Affiliation(s)
- Zhongxin Ma
- Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
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Asano Y, Yasukawa K. Identification and development of amino acid oxidases. Curr Opin Chem Biol 2019; 49:76-83. [DOI: 10.1016/j.cbpa.2018.10.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 10/16/2018] [Accepted: 10/22/2018] [Indexed: 12/23/2022]
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Avalos D, Sabuncu S, Mamounis KJ, Davidson VL, Moënne-Loccoz P, Yukl ET. Structural and Spectroscopic Characterization of a Product Schiff Base Intermediate in the Reaction of the Quinoprotein Glycine Oxidase, GoxA. Biochemistry 2019; 58:706-713. [PMID: 30605596 DOI: 10.1021/acs.biochem.8b01145] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The LodA-like proteins make up a recently identified family of enzymes that rely on a cysteine tryptophylquinone cofactor for catalysis. They differ from other tryptophylquinone enzymes in that they are oxidases rather than dehydrogenases. GoxA is a member of this family that catalyzes the oxidative deamination of glycine. Our previous work with GoxA from Pseudoalteromonas luteoviolacea demonstrated that this protein forms a stable intermediate upon anaerobic incubation with glycine. The spectroscopic properties of this species were unique among those identified for tryptophylquinone enzymes characterized to date. Here we use X-ray crystallography and resonance Raman spectroscopy to identify the GoxA catalytic intermediate as a product Schiff base. Structural work additionally highlights features of the active site pocket that confer substrate specificity, intermediate stabilization, and catalytic activity. The unusual properties of GoxA are discussed within the context of the other tryptophylquinone enzymes.
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Affiliation(s)
- Dante Avalos
- Department of Chemistry and Biochemistry , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Sinan Sabuncu
- Department of Biochemistry and Molecular Biology, School of Medicine , Oregon Health & Science University , Portland , Oregon 97239 , United States
| | - Kyle J Mamounis
- Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry and Molecular Biology, School of Medicine , Oregon Health & Science University , Portland , Oregon 97239 , United States
| | - Erik T Yukl
- Department of Chemistry and Biochemistry , New Mexico State University , Las Cruces , New Mexico 88003 , United States
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Yukl ET, Davidson VL. Diversity of structures, catalytic mechanisms and processes of cofactor biosynthesis of tryptophylquinone-bearing enzymes. Arch Biochem Biophys 2018; 654:40-46. [PMID: 30026025 PMCID: PMC6098718 DOI: 10.1016/j.abb.2018.07.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/10/2018] [Accepted: 07/13/2018] [Indexed: 11/20/2022]
Abstract
Tryptophyquinone-bearing enzymes contain protein-derived cofactors formed by posttranslational modifications of Trp residues. Tryptophan tryptophylquinone (TTQ) is comprised of a di-oxygenated Trp residue, which is cross-linked to another Trp residue. Cysteine tryptophylquinone (CTQ) is comprised of a di-oxygenated Trp residue, which is cross-linked to a Cys residue. Despite the similarity of these cofactors, it has become evident in recent years that the overall structures of the enzymes that possess these cofactors vary, and that the gene clusters that encode the enzymes are quite diverse. While it had been long assumed that all tryptophylquinone enzymes were dehydrogenases, recently discovered classes of these enzymes are oxidases. A common feature of enzymes that have these cofactors is that the posttranslational modifications that form the mature cofactors are catalyzed by a modifying enzyme. However, it is now clear that modifying enzymes are different for different tryptophylquinone enzymes. For methylamine dehydrogenase a di-heme enzyme, MauG, is needed to catalyze TTQ biosynthesis. However, no gene similar to mauG is present in the gene clusters that encode the other enzymes, and the recently characterized family of CTQ-dependent oxidases, termed LodA-like proteins, require a flavoenzyme for cofactor biosynthesis.
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Affiliation(s)
- Erik T Yukl
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32827, USA.
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Davidson VL. Protein-Derived Cofactors Revisited: Empowering Amino Acid Residues with New Functions. Biochemistry 2018; 57:3115-3125. [PMID: 29498828 DOI: 10.1021/acs.biochem.8b00123] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A protein-derived cofactor is a catalytic or redox-active site in a protein that is formed by post-translational modification of one or more amino acid residues. These post-translational modifications are irreversible and endow the modified amino acid residues with new functional properties. This Perspective focuses on the following advances in this area that have occurred during recent years. The biosynthesis of the tryptophan tryptophylquinone cofactor is catalyzed by a diheme enzyme, MauG. A bis-FeIV redox state of the hemes performs three two-electron oxidations of specific Trp residues via long-range electron transfer. In contrast, a flavoenzyme catalyzes the biosynthesis of the cysteine tryptophylquinone (CTQ) cofactor present in a newly discovered family of CTQ-dependent oxidases. Another carbonyl cofactor, the pyruvoyl cofactor found in classes of decarboxylases and reductases, is formed during an apparently autocatalytic cleavage of a precursor protein at the N-terminus of the cleavage product. It has been shown that in at least some cases, the cleavage is facilitated by binding to an accessory protein. Tyrosylquinonine cofactors, topaquinone and lysine tyrosylquinone, are found in copper-containing amine oxidases and lysyl oxidases, respectively. The physiological roles of different families of these enzymes in humans have been more clearly defined and shown to have significant implications with respect to human health. There has also been continued characterization of the roles of covalently cross-linked amino acid side chains that influence the reactivity of redox-active metal centers in proteins. These include Cys-Tyr species in galactose oxidase and cysteine dioxygenase and the Met-Tyr-Trp species in the catalase-peroxidase KatG.
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Affiliation(s)
- Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
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Andreo-Vidal A, Mamounis KJ, Sehanobish E, Avalos D, Campillo-Brocal JC, Sanchez-Amat A, Yukl ET, Davidson VL. Structure and Enzymatic Properties of an Unusual Cysteine Tryptophylquinone-Dependent Glycine Oxidase from Pseudoalteromonas luteoviolacea. Biochemistry 2018; 57:1155-1165. [PMID: 29381339 DOI: 10.1021/acs.biochem.8b00009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glycine oxidase from Pseudoalteromonas luteoviolacea (PlGoxA) is a cysteine tryptophylquinone (CTQ)-dependent enzyme. Sequence analysis and phylogenetic analysis place it in a newly designated subgroup (group IID) of a recently identified family of LodA-like proteins, which are predicted to possess CTQ. The crystal structure of PlGoxA reveals that it is a homotetramer. It possesses an N-terminal domain with no close structural homologues in the Protein Data Bank. The active site is quite small because of intersubunit interactions, which may account for the observed cooperativy toward glycine. Steady-state kinetic analysis yielded the following values: kcat = 6.0 ± 0.2 s-1, K0.5 = 187 ± 18 μM, and h = 1.77 ± 0.27. In contrast to other quinoprotein amine dehydrogenases and oxidases that exhibit anomalously large primary kinetic isotope effects on the rate of reduction of the quinone cofactor by the amine substrate, no significant primary kinetic isotope effect was observed for this reaction of PlGoxA. The absorbance spectrum of glycine-reduced PlGoxA exhibits features in the range of 400-650 nm that have not previously been seen in other quinoproteins. Thus, in addition to the unusual structural features of PlGoxA, the kinetic and chemical reaction mechanisms of the reductive half-reaction of PlGoxA appear to be distinct from those of other amine dehydrogenases and amine oxidases that use tryptophylquinone and tyrosylquinone cofactors.
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Affiliation(s)
- Andres Andreo-Vidal
- Department of Genetics and Microbiology, University of Murcia , Murcia 30100, Spain
| | - Kyle J Mamounis
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
| | - Esha Sehanobish
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
| | - Dante Avalos
- Department of Chemistry and Biochemistry, New Mexico State University , Las Cruces, New Mexico 88003, United States
| | | | - Antonio Sanchez-Amat
- Department of Genetics and Microbiology, University of Murcia , Murcia 30100, Spain
| | - Erik T Yukl
- Department of Chemistry and Biochemistry, New Mexico State University , Las Cruces, New Mexico 88003, United States
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
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