| Project/Area Number |
13125205
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
TETSUO Toraya Okayama University, Fac. of Engineering, Professor, 工学部, 教授 (70026318)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIO Hisaeda Kyushu University, Graduate School of Engineering, Professor, 大学院・工学研究院, 教授 (70150498)
MAMORU Yamanishi MAMORU,Yamanishi, 工学部, 助手 (30240063)
TAKAMASA Tobimatsu TAKAMASA,Tobimatsu, 工学部, 助教授 (30188768)
KASUNARI Yoshizawa Kyushu University, Inst. for Materials Chem. & Eng., Professor, 先導物質科学研究所, 教授 (30273486)
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| Project Period (FY) |
2001 – 2003
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| Keywords | vitamin B12 coenzyme / X-ray analysis / radical enzyme / diol dehydrates / theoretical calculation / density-functional-theory / composite catalyst / apoenzyme model |
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| Research Abstract |
1. Science of Cobalamin Enzymes and Their Improvement by Directed Evolution (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 distorted to some extent. (4)Coenzymic activity of cobalamin analogs in which the base moiety of the coezyme B_<12> 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
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with B_<12> and R-or S-enantiomer were analyzed. The stereochemical courses of all the steps of the conversion of each enantiomeric substrate to product were completely elucidated based on the X-ray structures. (6)The results obtained by this study were summarized and published as a review in Chemical Reviews, the world-most authoritative review journal in Chemistry.
2. Elucidation of Enzyme Mechanism by Theoretical Chemistry (1)Each step of diol dehydratase reaction was demonstrated to be energetically feasible by density-functional-theory computations with a simple model. (2)lmportant contributions of Glu170 and His 143 in the OH group migration in diol dehydratase reaction were demonstrated by means of a quantum mechanical/molecular mechanical method with a whole enzyme model including all the atoms except hydrogens.
3. Construction of B_<12> Composite Catalysts (1)Composite catalysts constructed by combination of B_<12> and apoenzyme models, such as synthetic peptide-1ipids, lipid bilayers, and inorganic polymer matrices, were demonstrated to be highly reactive in carbon-skeleton rearrangement and dehalogenation reactions. (2)An enzyme model containing B_<12> and crown compounds was synthesized, and its capability to bind K^+ was confirmed. Less
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