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: 7803563
• 负责人: KURT WARNCKE
• 金额: $ 29.46万
• 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 2013-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7803563
• 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; Escape Reaction; Ethanolamine Ammonia-Lyase; Event; Free Energy; Free Radicals; Freezing; Funding; Generations; Genetic Recombination; Goals; 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; 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; mutant; novel; novel strategies; photolysis; programs; public health relevance; 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）： 利用电子缺陷自由基物种极端反应性的酶进行了生物学中最困难的化学反应。这些酶实现的区域和立体观念违反了根本反应是非特异性的长期观念。 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（腺苷泡）依赖性酶超家族，其成员催化代谢物的共价重排。这些化学分离的催化剂中的常见主要步骤是金属辅助的电子缺陷有机自由基的产生。该引发剂自由基本身或通过二级自由基物种促进了从底物中促进氢原子的抽象，从而形成了底物基自由基，开了一个新的反应通道，以促进对产物的转化。一个杰出的问题是，如何针对快速重组稳定自由基对以高产量实现生产反应。阐明蛋白质和辅因子指导产生，稳定，蛋白质内部迁移和自由基重排的基本原理将受到拟议研究的持续重点。已选择辅酶B12依赖性酶和乙醇胺氨 - 洛酶进行审查。将使用脉冲 - 电子顺磁共振共鸣的技术和可见的/近红外吸收光谱，在冷冻和时间分辨的系统中使用脉冲和时间分辨的系统，在picoseconds到小时。开发的基本见解和新方法将促进对其他生物反应中自由基中间体的识别和表征，为程序性自由基反应性设计提供信息，并有助于分子治疗性努力来对抗有害自由基的自由基过程。公共卫生相关性：利用电子缺陷自由基的极端反应性的酶执行生物学中最困难的反应。我们试图通过使用光谱技术来理解辅酶B12依赖性酶对这种生产性自由基反应性的贡献。开发的基本见解和新方法将促进其他生物系统中自由基中间体的表征，为程序性自由基反应性的设计提供信息，并协助分子治疗努力以对抗有害自由基的有害自由基过程。