Determining the structural basis for the mechanism of catalytic O2 evolution by t

通过 t 确定催化 O2 析出机制的结构基础

• 批准号: 7941664
• 负责人: Gudrun Susanne Lukat-Rodgers
• 金额: $ 43.05万
• 依托单位: NORTH DAKOTA STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7941664
• 关键词: Arginine; Automobile Driving; Binding; Biological; Biology; Characteristics; Charge; Chlorine; Complex; Computer Systems Development; Dependence; Deuterium; Development; Distal; Electronics; Electrons; Electrostatics; Enzymes; Evolution; Foundations; Freezing; Frequencies; Goals; Heme; Heme Iron; Hydrogen Bonding; Hypochlorite; Ions; Isotope Labeling; Kinetics; Knowledge; Label; Ligand Binding; Ligands; Medical; Mutation; Nature; Organism; Oxidation-Reduction; Oxygen; Peracetic Acid; Play; Positioning Attribute; Property; Raman Spectrum Analysis; Reaction; Role; Scheme; Side; Specificity; Spectrum Analysis; Stretching; Structure; Suggestion; System; Technology; Testing; Work; analog; base; chlorite; electronic structure; enzyme substrate; ground water; heme a; mutant; pollutant; protonation; public health relevance; research study; wasting

DESCRIPTION (provided by applicant): The heme-containing enzyme commonly known as chlorite dismutase (Cld) catalyzes the unimolecular decomposition of chlorite ion, ClO2-, as illustrated in Scheme 1. The reaction is thought to proceed via formation of compound I (2) through a heme-catalyzed isomerization of O-bound chlorite, FeIIIClO2-, to coordinated peroxyhypochlorite, FeIII-OOCl- (3), followed by an intramolecular redox reaction that releases O2, and Cl-. Recent spectroscopic and kinetic work has led to the suggestion that the catalytic mechanism proceeds through a two-electron oxidized heme intermediate having properties characteristic of compound I (Cpd-I). Its formation is thought to occur with release of the two-electron reduced fragment, hypochlorite, which recombines with the yl-oxygen atom of Cpd-I to yield a peroxyhypochlorite complex. This complex is unstable with respect to release of O2 and Cl-. Reactions that evolve O2 are rare in biology, with that catalyzed by the O2-evolving tetranuclear Mn cluster of PSII being the only other known example. The precise nature of the Cld intermediates and the modulation of their reactivities by the enzyme remain to be elucidated. The overarching goal of this work is to clarify the structural basis for the spectacular catalytic efficiency and mechanistic specificity of this unique O2-evolving reaction. The specific aims focus on spectroscopic (primarily resonance Raman, rR) and kinetic (freeze-quench) approaches to determining atom connectivities, structures and electronic properties of intermediates in the catalytic decomposition of ClO2- by Cld from Dechloromonas aromatica RCB. Specifically, this proposed project aims to: 1. further clarify the roles of distal pocket residues in directing substrate binding and Cl-O bond scission to yield Cpd-I. 2. probe the nonbonded interactions between the ferryl moiety of the Cpd-I intermediate and the distal pocket in the freeze quenched reaction of ferric Cld with peracetic acid by resonance Raman spectroscopy. 3. probe structure and bonding in the first catalytic intermediate in the reaction between ferric Cld and the substrate, ClO2-. 4. investigate the structural and electronic properties of the rebounded state. PUBLIC HEALTH RELEVANCE: The goal of this project is to build a basic understanding of how biological organisms make the oxygen that we breath. This knowledge will provide the foundation for development of medical and materials technologies for specialized oxygen delivery systems. It can also be applied to the development of systems for removing toxic chlorine-based pollutants from waste and ground water.

描述（由申请人提供）：含血红素的酶通常称为血红素歧化酶（Cld），催化血红素离子ClO 2-的单分子分解，如方案1所示。该反应被认为是通过血红素催化的O-键合的FeIIIClO 2-异构化形成化合物I（2），形成配位的过氧次氯酸盐， FeIII-OOCl-（3），随后发生分子内氧化还原反应，释放O2和Cl-。 最近的光谱和动力学工作已经导致的建议，催化机制进行通过一个两电子氧化血红素中间体具有化合物I（Cpd-I）的特性。它的形成被认为是随着释放双电子还原片段次氯酸盐而发生的，次氯酸盐与Cpd-I的yl-氧原子重新结合以产生过氧次氯酸盐络合物。 该络合物对于O2和Cl-的释放是不稳定的。释放O2的反应在生物学中是罕见的，由PSII的释放O2的四核Mn簇催化的反应是唯一的其他已知例子。Cld中间体的确切性质和酶对它们的反应性的调节仍有待阐明。这项工作的首要目标是澄清壮观的催化效率和机制的特异性，这种独特的O2-进化反应的结构基础。具体目标集中在光谱（主要是共振拉曼，rR）和动力学（冷冻淬灭）的方法来确定Cld从Dechloromonasaromatica RCB催化分解ClO 2-的中间体的原子连接性，结构和电子性质。具体而言，本拟议项目旨在：1.进一步阐明了远端口袋残基在指导底物结合和Cl-O键断裂以产生Cpd-I中的作用。2.用共振拉曼光谱法研究了Cld与过氧乙酸冷冻猝灭反应中Cpd-I中间体的铁基部分与远端口袋之间的非键相互作用。3.探针结构和在铁Cld与底物ClO 2-反应的第一催化中间体中的键合。4.研究反弹态的结构和电子性质。 公共卫生相关性：这个项目的目标是建立一个基本的了解生物有机体如何使我们呼吸的氧气。这些知识将为专业氧气输送系统的医疗和材料技术的发展提供基础。它还可用于开发从废水和地下水中去除有毒氯基污染物的系统。