Enzymology of the reductive acetyl-CoA pathway

还原乙酰辅酶A途径的酶学

• 批准号: 7600463
• 负责人: Stephen Wiley Ragsdale
• 金额: $ 32万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-08-01 至 2012-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7600463
• 关键词: Acetates; Acetyl Coenzyme A; Acids; Active Sites; Area; Bacteria; Binding; Biochemistry; Biology; C-terminal; Carbon; Carbon Dioxide; Carbon Monoxide; Carbon monoxide dehydrogenase; Catalysis; Chemicals; Cobalamin; Coenzyme A; Competence; Complex; Corrinoids; Coupling; Electron Transport; Environment; Enzymatic Biochemistry; Enzymes; Exhibits; Fostering; Freezing; Gases; Ions; Iron-Sulfur Proteins; Kinetics; Metals; Methanobacteria; Methods; Methyltransferase; Microbe; Microbiology; Molecular Conformation; Molecular Structure; Organism; Oxidation-Reduction; Pathway interactions; Physiological; Play; Property; Proteins; Protons; Pyruvate synthase; Reaction; Research Proposals; Role; Site; Staging; Structure; System; Testing; Time; Variant; Wood material; Work; adduct; analog; base; catalyst; insight; meter; multidisciplinary; novel; oxidation; protein protein interaction; protonation; research study; uptake

DESCRIPTION (provided by applicant): This research application focuses on mechanistic studies of three key enzymes in the Wood-Ljungdahl pathway: CO dehydrogenase/acetyl-CoA synthase (CODH/ACS), methyltransferase (MeTr), and the corrinoid iron-sulfur protein (CFeSP). Studies on this system have enriched the areas of microbiology, biochemistry, and metallobiochemistry in revealing the structures of macromolecular channels and previously unknown metal clusters. These studies are providing insight into how these proteins use bioorganometallic intermediates in catalyzing group transfer reactions and C-C and C-S bond formation and cleavage allowing organisms to assimilate carbon dioxide and the toxic gas, CO. This system serves as a paradigm for understanding bioinorganic chemical principles, complex protein-protein interactions, and how proteins coordinate redox reactions with chemical catalysis. The major focus of this application is on multidisciplinary structure-functions studies of the three major classes of Ni-CODHs: the monofunctional CODH, the bifunctional CODH/ACS from acetogenic bacteria, and the bifunctional CODH/ACS (also called acetyl-CoA decarbonylase synthase, ACDS) from aceticlastic methanogens. Because these enzymes play different physiological roles, they are hypothesized to exhibit correspondingly disparate catalytic properties, including different mechanisms of substrate channeling, catalytic biases for CO oxidation/carbon dioxide reduction, and electrochemical properties. The proton transfer network including the acid-base catalyst(s), conserved among all CODH classes, will be further investigated. The early intermediate(s) in the CODH mechanism will be trapped and characterized. The internal electron transfer reaction in the ACS mechanism will be characterized. We will further investigate how the CO channel in CODH/ACS meters the supply of and demand for CO and investigate how the CODH and ACS sites in CODH/ACS are coordinated. We also will determine the crystal structure of the CFeSP- MeTr complex and investigate the proposed role of a major conformational change in the reaction of MeTr with the CFeSP. Studies on PFOR will test a kinetic coupling hypothesis, including identification of a proposed radical species formed by reaction of CoA with the hydroxyethyl-TPP radical. PUBLIC HEALTH RELEVANCE: We are studying the key enzymes in a pathway by which anaerobic microbes assimilate carbon dioxide and carbon monoxide. These studies involve the elucidating new roles of metal ions in biology (metal-carbon bonds, new heterometallic clusters, and nucleophilic metal ions), characterizing novel substrate-derived radical intermediates, and describing channels for gaseous substrates within an enzyme.

描述（由申请人提供）：本研究申请的重点是木材ljungdahl途径中三种关键酶的机理研究：CO脱氢酶/乙酰基-COA合酶（CODH/ACS），甲基转移酶（METR）和阳性型铁素铁硫蛋白（CFESP）（CFESP）。对该系统的研究丰富了微生物学，生物化学和金属生物化学的领域，以揭示大分子通道的结构和以前未知的金属簇的结构。这些研究提供了有关这些蛋白质如何在催化群体转移反应以及C-C和C-S键形成和切割的C-C-C-S键形成和切割中如何使用生物学金属中间体的见解催化。该应用的主要重点是对三个主要类别的Ni-Codhs的多学科结构 - 功能研究：单功能CODH，来自乙型细菌的双功能CODH/ACS，以及双功能CODH/ACS（也称为乙酰-COA coA coa coa coa decarbonylase synthase assythase，Acds，Acds）。由于这些酶扮演着不同的生理作用，因此假设它们表现出相应的不同催化特性，包括底物通道的不同机制，用于CO氧化/还原二氧化碳的催化偏置和电化学性质。质子转移网络包括所有CODH类别中保守的酸碱催化剂，将进一步研究。 CODH机制中的早期中间体将被困和表征。 ACS机制中的内部电子转移反应将被表征。我们将进一步研究CODH/ACS中的CO渠道如何供应CO的供应和需求，并研究CODH/ACS中的CODH和ACS站点如何协调。我们还将确定Cfesp-Metr复合物的晶体结构，并研究METR与CFESP反应的主要构象变化的拟议作用。 PFOR的研究将检验一个动力学耦合假设，包括鉴定由COA与羟基乙基TPP自由基反应形成的提出的激进物种。公共卫生相关性：我们正在研究厌氧微生物吸收二氧化碳和一氧化碳的途径中的关键酶。这些研究涉及金属离子在生物学中的新作用（金属 - 碳键，新的杂化簇和亲核金属离子），表征了新型底物衍生的自由基中间体，并描述了酶内气态底物的通道。