Co(II)-Radical Pair Dynamics in B12 Enzyme Catalysis

B12 酶催化中的 Co(II)-自由基对动力学

基本信息

批准号：
7564374
负责人：
KURT WARNCKE
金额：
$ 5.93万
依托单位：
EMORY UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1998
资助国家：
美国
起止时间：
1998-03-15 至 2008-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7564374
关键词：
Active Sites Address Amines Aspirin Binding Biological Biology Carbon Catalysis Cell Nucleus Class Classification Cobalamin Cobalt Coenzymes Complex Coupled DNA Sequence Rearrangement DNA biosynthesis Development Electron Nuclear Double Resonance Electron Spin Resonance Spectroscopy Electrons Enzymes Ethanolamine Ammonia-Lyase Event Free Radicals Freezing Frequencies Funding Generations Genetic Recombination Goals Hour Hydration status Hydrogen Hydrogen Bonding Kinetics Lasers Ligands Liquid substance Measurement Measures Mediating Metals Methods Methylmalonyl-CoA Mutase Molecular Molecular Structure Nitrogen Non-Steroidal Anti-Inflammatory Agents Nuclear Object Attachment Optics Oxidation-Reduction Phase Physiologic pulse Powder dose form Preparation Process Prostaglandin-Endoperoxide Synthase Protein Dynamics Proteins Protons Pulse taking Quantum Mechanics Range Reaction Research Ribonucleotide Reductase Roentgen Rays Role Solid Solvents Spectrum Analysis Spin Labels Structure System Techniques Temperature Testing Therapeutic Time absorption aqueous chemical reaction cobamamide cofactor corrin covalent bond design enzyme structure insight member metalloenzyme migration molecular mechanics mutant novel photolysis programs research study solid state three dimensional structure

项目摘要

Enzymes that harness the extreme reactivity of electron-deficient free radical species carry out some of the most difficult chemical reactions in biology. The regio- and stereo-selectivity achieved by these enzymes defies long-held ideas that radical reactions are non-specific. This class includes the following: ribonucleotide reductases, which catalyze the first unique step in DNA biosynthesis, prostaglandin H-synthase, the target of aspirin and other nonsteroidal anti-inflammatory drugs, the S-adenosylmethionine-dependent enzymes, with over six-hundred members that catalyze a wide range of radicalmediated redox reactions, and the coenzyme B12 (adenosylcobalamin)-dependent enzyme superfamily, whose members catalyze metabolite covalent bond rearrangements. The common primary step in these chemically-disparate catalyses is metal-assisted generation of an electron-deficient organic radical. This initiator radical, either by itself or through secondary radical species, promotes hydrogen atom abstraction from the substrate to form a substratebased radical, opening a new reaction channel that facilitates transformation to the product. An outstanding issue is how the radical pair is stabilized against rapid recombination to achieve productive reaction in high yield. Elucidating the basic principles of how protein and cofactor guide radical generation, stabilization, intra-protein radical migration, and radical rearrangement will be sustained focuses of the proposed studies. The coenzyem B12-dependent enzymes, and ethanolamine ammonia-lyase specifically, have been selected for scrutiny. The contributions of molecular structure and dynamics to enzyme function will be studied by using techniques of pulsed-electron paramagnetic resonance and visible/near-infrared absorption spectroscopy, in cryotrapped and time-resolved systems on time scales ranging from picoseconds to hours. The fundamental insights and novel methods developed will promote identification and characterization of radical intermediates in other biological reactions, inform the design of programmed radical reactivity, and assist molecular-therapeutic efforts to combat pernicious free radical processes.

利用缺电子自由基的极端反应性的酶物种进行生物学中一些最困难的化学反应。这这些酶实现的区域选择性和立体选择性违背了长期以来的想法自由基反应是非特异性的。该类包括以下内容：核糖核苷酸还原酶，催化 DNA 中第一个独特的步骤生物合成、前列腺素 H 合酶、阿司匹林和其他非类固醇的靶标抗炎药，S-腺苷甲硫氨酸依赖性酶，拥有超过六百个成员，可催化广泛的自由基介导的氧化还原反应和辅酶 B12（腺苷钴胺素）依赖性酶超家族，其成员催化代谢物共价键重新安排。这些化学性质不同的过程中共同的初级步骤催化是金属辅助产生缺电子有机自由基。该引发剂自由基，无论是其本身还是通过次级自由基物质，促进氢原子从底物中提取，形成基于底物的激进，开辟新的反应通道，促进转化产品。一个悬而未决的问题是激进货币对如何稳定下来快速重组以实现高产率的生产反应。阐明蛋白质和辅因子如何引导自由基产生的基本原理，稳定性、蛋白质内自由基迁移和自由基重排将拟议研究的持续重点。辅酶 B12 依赖性酶，特别是乙醇胺氨裂解酶，已被选择用于审查。分子结构和动力学对酶的贡献将使用脉冲电子顺磁技术来研究功能共振和可见/近红外吸收光谱，在冷冻陷阱中时间尺度从皮秒到小时的时间分辨系统。所开发的基本见解和新颖方法将促进其他生物中自由基中间体的鉴定和表征反应，为程序化自由基反应的设计提供信息，并协助对抗有害自由基过程的分子治疗努力。