MODEL STUDIES OF ACETYL COENZYME A SYNTHASE

乙酰辅酶A合酶的模型研究

• 批准号: 6636291
• 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 2005-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6636291
• 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.

拟议的研究旨在阐明使用含镍的乙酰辅酶A合成酶（ACS）使用明确定义的低分子量系统催化的基本步骤的机械参数。 其中包括在这些步骤中包括将甲基从甲基蛋白（C/Fe-SP）转移到簇的酶，将CO插入CH3-A簇键，并加入CH3C（O）-A簇中的硫醇酸盐。 为此，首先需要准备包含催化位点（群集）关键特征的合成类似物。与所有光谱数据一致的结构模型（不可用X射线结构）包括通过共价桥X连接到[FE3S4] 2+簇的（N/O）2S2供体环境中的单个镍离子。 化学反应性研究将需要使用合成类似物进行化学计量变化。 使用机械无机化学方案，包括产品分析，动力学测量，立体化学和激进的时钟探测器研究，将系统询问个别反应。 该项目的长期目标是对生物异量化簇的结构，电子和化学特性如何优化针对预期的催化转化进行优化。拟议的研究影响了我们对基本痕量元素镍的生物学意义的理解，这些镍包括幽门螺杆菌的活力，与幽门螺杆菌疾病，胃癌和胃淋巴瘤有关，以及通过产生去脱脂DNA的氧化物种而产生的癌变。 另外，含有AC的生物体乙酸和甲烷植物细菌对人的消化功能和功能障碍可能很重要，因为它们占据了大量的结肠。 从更广泛的角度来看，对ACS的深入了解对于我们对一般生物异质金属组件的一般类别的基本了解，例如[Nife]氢化酶，亚硫酸盐还原酶，细胞色素C氧化酶，[Cuzn]超氧化物歧化酶和氮酶辅助因子中的催化位点。