MODEL STUDIES OF ACETYL COENZYME A SYNTHASE

乙酰辅酶A合酶的模型研究

• 批准号: 6727647
• 负责人: CHARLES G. RIORDAN
• 金额: $ 15万
• 依托单位: UNIVERSITY OF DELAWARE
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6727647
• 关键词: X ray crystallography; acetyl coA; acid thiol ligase; active sites; catalyst; chemical bond; chemical structure function; electron transport; electrospray ionization mass spectrometry; enzyme activity; enzyme structure; gas chromatography mass spectrometry; infrared spectrometry; interferometry; iron compounds; metal complex; nickel; nuclear magnetic resonance spectroscopy; peptide chemical synthesis; physical model

The proposed research is designed to elucidate the mechanistic parameters of the elementary steps catalyzed by the nickel- containing acetyl-coenzyme A synthase (ACS) using well-defined low molecular weight systems. Included among these steps are the nonenzymatic transfer of a methyl group from the corrinoid protein (C/Fe-SP) to the A cluster, CO insertion into the CH3-A cluster bond and thiolate addition to the CH3C(O)-A cluster. To this end, first it will be necessary to prepare synthetic analogs that contain the key features of the catalytic site (A cluster). A structural model consistent with all spectroscopic data (an X- ray structure is not available) includes a single nickel ion in a (N/O)2S2 donor environment linked through a covalent bridge, X, to an [Fe3S4]2+ cluster. Chemical reactivity studies will entail probing stoichiometric transformations using the synthetic analogs. Individual reactions will be systematically interrogated using the protocols of mechanistic inorganic chemistry including product analyses, kinetic measurements, stereochemical and radical clock probe investigations. The long- term goal of this project is to develop a detailed mechanistic understanding of how the structural, electronic and chemical properties of biological heterometallic clusters are optimized for the intended catalytic transformations. The proposed research impacts our understanding of the biological implications of the essential trace element nickel that include the virility of Helicobacter pylori which has been associated with peptic ulcer disease, gastric carcinoma, and gastric lymphoma, and carcinogenesis through production of oxidizing species that degrade DNA. Additionally, acetongenic and methanogenic bacteria, organisms that contain ACS, may be important to human digestive function and dysfunction as they occupy a large volume of the colon. More broadly, a deeper understanding of ACS is valuable to our fundamental understanding of the general class of biological heterometallic assemblies, e.g. the catalytic sites in [NiFe] hydrogenase, sulfite reductase, cytochrome c oxidase, [CuZn] superoxide dismutase and the nitrogenase cofactor.

拟议的研究旨在使用明确的低分子量系统阐明含镍乙酰辅酶 A 合酶 (ACS) 催化的基本步骤的机械参数。 这些步骤包括甲基从类咕啉蛋白 (C/Fe-SP) 到 A 簇的非酶转移、CO 插入 CH3-A 簇键以及硫醇盐添加到 CH3C(O)-A 簇。 为此，首先需要制备包含催化位点（A簇）关键特征的合成类似物。与所有光谱数据一致的结构模型（X 射线结构不可用）包括 (N/O)2S2 供体环境中的单个镍离子，通过共价桥 X 连接到 [Fe3S4]2+ 簇。 化学反应性研究将需要使用合成类似物探测化学计量变换。 将使用机械无机化学协议系统地询问各个反应，包括产物分析、动力学测量、立体化学和自由基时钟探针研究。 该项目的长期目标是对如何优化生物异金属簇的结构、电子和化学性质以实现预期的催化转化形成详细的机制理解。拟议的研究影响了我们对必需微量元素镍的生物学意义的理解，其中包括与消化性溃疡病、胃癌和胃淋巴瘤有关的幽门螺杆菌的活力，以及通过产生降解 DNA 的氧化物质而致癌的作用。 此外，产丙酮和产甲烷细菌（含有 ACS 的生物体）可能对人类消化功能和功能障碍很重要，因为它们占据了结肠的大部分体积。 更广泛地说，对 ACS 的更深入了解对于我们对一般类别的生物异金属组件（例如生物异金属组件）的基本理解很有价值。 [NiFe]氢化酶、亚硫酸盐还原酶、细胞色素c氧化酶、[CuZn]超氧化物歧化酶和固氮酶辅因子中的催化位点。