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

B12 酶催化中的 Co(II)-自由基对动力学

• 批准号: 8266392
• 负责人: KURT WARNCKE
• 金额: $ 26.43万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-15 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8266392
• 关键词: Address; Amines; Amino Acids; Anti-Inflammatory Agents; Anti-inflammatory; Aspirin; Biological; Biology; Carbon; Catalysis; Cobalt; Complex; Coupled; DNA Sequence Rearrangement; DNA biosynthesis; Dependence; Development; Electron Nuclear Double Resonance; Electron Spin Resonance Spectroscopy; Electrons; Entropy; Enzymes; Enzymes and Coenzymes; Escape Reaction; Ethanolamine Ammonia-Lyase; Event; Free Energy; Free Radicals; Freezing; Funding; Generations; Genetic Recombination; Goals; Health; Home environment; Hour; Hydration status; Hydrogen; Hydrogen Bonding; Isotopes; Kinetics; Label; Lasers; Liquid substance; Measurement; Measures; Mediating; Metals; Methods; Methylmalonyl-CoA Mutase; Modeling; Molecular; Molecular Structure; Monitor; Optics; Oxidation-Reduction; Pharmaceutical Preparations; Phase; Physiologic pulse; Powder dose form; Preparation; Process; Prostaglandin-Endoperoxide Synthase; Protein Dynamics; Proteins; Protons; Reaction; Relative (related person); Research; Research Personnel; Resolution; Ribonucleotide Reductase; S-Adenosylmethionine; Salmonella typhimurium; Side; Solid; Solutions; Solvents; Spectrum Analysis; Structure; Sucrose; System; Techniques; Temperature; Testing; Therapeutic; Thermodynamics; Time; absorption; aqueous; base; biological systems; chemical reaction; cobamamide; coenzyme B; cofactor; combat; covalent bond; design; enthalpy; insight; instrument; member; metalloenzyme; migration; molecular dynamics; mutant; novel; novel strategies; photolysis; programs; research study; simulation; three dimensional structure

DESCRIPTION (provided by applicant): 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 non- steroidal anti-inflammatory drugs, the S-adenosylmethionine-dependent enzymes, with over six-hundred members that catalyze a wide range of radical- mediated 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 substrate- based 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 coenzyme 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. PUBLIC HEALTH RELEVANCE: Enzymes that harness the extreme reactivity of electron-deficient free radicals perform some of the most difficult reactions in biology. We seek to understand the contributions of molecular structure and dynamics to this productive radical reactivity in coenzyme B12-dependent enzymes by using spectroscopic techniques. The fundamental insights and novel approaches developed will promote characterization of radical intermediates in other biological systems, inform the design of programmed radical reactivity, and assist molecular- therapeutic efforts to combat pernicious free radical processes.

描述（由申请人提供）： 利用缺电子自由基物种的极端反应性的酶可以进行生物学中一些最困难的化学反应。这些酶所实现的区域选择性和立体选择性违背了自由基反应是非特异性的长期观念。此类包括以下酶：核糖核苷酸还原酶（催化 DNA 生物合成中第一个独特步骤）、前列腺素 H 合酶（阿司匹林和其他非甾体类抗炎药的靶标）、S-腺苷甲硫氨酸依赖性酶（拥有 600 多个成员，可催化广泛的自由基介导的氧化还原反应）以及辅酶 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排。这些化学上不同的催化的共同主要步骤是金属辅助生成缺电子有机自由基。该引发剂自由基本身或通过次级自由基物质促进氢原子从底物中提取，形成基于底物的自由基，从而打开新的反应通道，促进向产物的转化。一个突出的问题是如何稳定自由基对以防止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指导自由基产生、稳定、蛋白质内自由基迁移和自由基重排的基本原理将是拟议研究的持续重点。辅酶 B12 依赖性酶，特别是乙醇胺解氨酶，已被选中进行详细检查。将通过脉冲电子顺磁共振和可见/近红外吸收光谱技术，在皮秒到小时的时间尺度上的冷冻和时间分辨系统中研究分子结构和动力学对酶功能的贡献。所开发的基本见解和新颖方法将促进其他生物反应中自由基中间体的识别和表征，为编程自由基反应的设计提供信息，并协助分子治疗努力对抗有害的自由基过程。公共健康相关性：利用缺电子自由基的极端反应性的酶可以执行生物学中一些最困难的反应。我们试图通过使用光谱技术来了解分子结构和动力学对辅酶 B12 依赖性酶中这种产生自由基反应的贡献。所开发的基本见解和新颖方法将促进其他生物系统中自由基中间体的表征，为编程自由基反应的设计提供信息，并协助分子治疗努力对抗有害的自由基过程。