Mechanisms of Radical Catalysis in Vitamin B_<12> Enzyme and Reactivation by Molecular Chaperone-like Factor

维生素B_<12>酶的自由基催化机制及类分子伴侣因子的再激活

• 批准号: 13480195
• 负责人: TORAYA Tetsuo
• 金额: $ 5.95万
• 依托单位: OKAYAMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13480195/
• 关键词: vitamin B12 coenzyme; radical enzyme; reactivation; molecular chaperone; X-ray analysis; theoretical calculation; mechanism-based inactivation; diol dehydratase; 再活性化因子; エタノールアミンアンモニアリアーゼ; 自殺不活性化; ビタミンB_<12>

1.Mechanism of radical catalysis by vitamin B12 enzymes(1) Recombinant glycerol dehydratase was purified, and its enzymological properties were investigated. Its X-ray structure was solved for the first time. (2) The formation of the adenine-anchored radical was crystallographically demonstrated upon illumination of the diol dehydratase-adeninylpentylcobalamin complex with visible light. (3) The structure of substrate-free form of diol dehydratase was determined. It was strongly suggested that substrate triggers the homolysis of the coenzyme Co-C bond by inducing further steric strain to the Co-C bond that had been already strained to some extent. (4) Coenzymic activity of coenzyme analogs in which the base moiety of the coezyme B12 was replaced by other bases was correlated with the bulkiness of the base. It was also suggested that the nucleotide moiety is required for stabilizing radical intermediates. (5) The X-ray structures of the complexes of diol dehydratase with B12 and R-or S- … More enantiomer were analyzed, and The stereochemical _courses of the steps of the conversion of each enantiomeric substrate to product was completely elucidated based on the X-ray structures. (6) Theoretical calculations with a simplified model indicated that the activation energies of each steps of diol dehydratase reaction are small enough to be supplied by substrate binding energy.2. Mechanism of reactivation of a B12 enzyme by molecular chaperone-like Factor(1) The two ORFs near the glycerol dehydratase genes were identified as putative reactivating factor genes. The purified gene products actually reactivated the inactivated holoenzyime by a molecular chaperone-like manner. (2) The gene encoding a reactivating factor for ethanolamine ammonia-lyric was identified. The purified gene product was shown to serve as a reactivating factor in the presence of B12 coenzyme and ATP.The results obtained by this study was summarized and published as a review in the special issue of "Radical Enzymology" in Chemical Reviews. The fact that I was invited to write this review for this most authoritative journal in chemistry indicates that the scientific merit of this study rated excellent among the international community in this field. Less

1.维生素B12酶自由基催化机理的研究（1）重组甘油脱氢酶的纯化及其酶学性质的研究。它的X射线结构首次得到解决。(2)腺嘌呤锚定的自由基的形成，晶体学证明后，用可见光照射的二醇脱氢酶-腺嘌呤戊钴胺素复合物。(3)确定了无底物形式的二醇脱氢酶的结构。这强烈表明，底物通过诱导已经在一定程度上应变的Co-C键的进一步空间应变来触发辅酶Co-C键的均裂。(4)辅酶B12的碱基部分被其他碱基取代的辅酶类似物的辅酶活性与碱基的体积相关。也有人建议，核苷酸部分是需要稳定自由基中间体。(5)二醇脱氢酶与B_（12）和R-或S-复合物的X射线结构 ...更多信息 对映体进行了分析，并根据X射线结构完整地阐明了各对映体底物转化为产物步骤的立体化学过程。(6)简化模型的理论计算表明，二醇脱氢酶反应各步的活化能都很小，可以由底物结合能提供.分子伴侣样因子激活B12酶的机制（1）甘油脱氢酶基因附近的两个开放阅读框被鉴定为可能的激活因子基因。纯化的基因产物实际上通过分子伴侣样方式重新激活了失活的全酶。(2)鉴定了乙醇胺解氨再活化因子的基因。纯化的基因产物在B12辅酶和ATP存在下显示出作为再活化因子的作用。本研究所获得的结果被总结并作为评论发表在《化学评论》的“自由基酶学”特刊上。事实上，我被邀请为这本最权威的化学杂志撰写这篇评论，表明这项研究的科学价值在国际社会在这一领域中被评为优秀。少

项目成果

虎谷哲夫: "廣川タンパク質化学 第4巻 酵素"廣川書店. 12, 17 (2003, 2004)

虎谷哲夫：《广川蛋白质化学第 4 卷酶》广川书店 12、17（2003 年、2004 年）。

Toraya, T., Eda, M., Kamachi, T., Yoshizawa, K: "Energetic Feasibility of Hydrogen Abstraction and Recombination in Coenzyme B_<12r>dependent Diol Dehydratase Reaction"Journal of Biochemistry. 130. 865-872 (2001)

Toraya, T.、Eda, M.、Kamachi, T.、Yoshizawa, K：“辅酶 B_12r> 依赖性二醇脱水酶反应中氢提取和重组的能量可行性”生物化学杂志。

Fukuoka, M., et al.: "Functions of the D-Ribosyl Moiety and the Lower Axial Ligand of the Nucleotide Loop of Coenzyme B12 in Diol Dehydratase and Ethanolamine Ammonia-lyase Reactions."J.Biochem.-Tokyo. 132(6). 935-943 (2002)

Fukuoka, M., et al.：“二醇脱水酶和乙醇胺氨裂解酶反应中辅酶 B12 核苷酸环的 D-核糖基部分和下轴配体的功能”。J.Biochem.-Tokyo。

Shibata, N., Masuda, J., Morimoto, Y., Yasuoka, N., Toraya, T.: "Substrate-Induced Conformational Change of a Coenzyme B12-Dependent Enzyme : Crystal Structure of the Substrate-Free Form of Diol Dehydratase"Biochemistry. 41(42). 12607-12617 (2002)

Shibata, N.、Masuda, J.、Morimoto, Y.、Yasuoka, N.、Toraya, T.：“辅酶 B12 依赖性酶的底物诱导构象变化：二醇脱水酶无底物形式的晶体结构

Fukuoka, M., Yamanishi, M., Zou, X., Brown, L.K., Toraya, T.et al.: "Functions of the D-Ribosyl Moiety and the Lower Axial Ligand of the Nucleotide Loop of Coenzyme B12 in Diol Dehydratase and Ethanolamine Ammonia-lyase Reactions"J. Biochem.. 132(6). 935-

Fukuoka, M.、Yamanishi, M.、Zou, X.、Brown, L.K.、Toraya, T.等人：“二醇脱水酶中辅酶 B12 核苷酸环的 D-核糖基部分和下轴配体的功能