Molecular Design and Evolution Engineering for Compositc Biochatalysts

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Structures and functions of composite biocatalysts were studied, and novel composite biocatalysts were constructed. Toraya et al. established a refined catalytic mechanism for cobalamin-dependent diol dehydratase based on its three-dimensional structure and demonstrated its energetic feasibility by theoretical calculations. Reactivity of the enzyme was modified by protein engineering techniques. Cobalamin composite catalysts were constructed using several apoenzyme models. Tanizawa et al. elucidated the molecular mechanism of biosynthesis and catalytic function of the topaquinone cofactor that is contained in copper amine oxidase and produced from a specific tyrosine residue. Furthermore, a new tryptophan-derived quinone cofactor, cysteine tryptophylquinone, in quinohemoprotein amine dehydrogenase was identified. Miura et al. obtained flavoenzymes with novel reactivity by incorporating artificial flavins to flavoenzyme apoproteins. Horiike et al. revealed molecular bases for substrate specificity of extradiol dioxygenases and 0_2 activation by these enzymes. Hayashi et al. elucidated the refined catalytic reaction mechanisms of pyridoxal enzymes by analyzing the proton-transfer process, thereby presenting the molecular understanding of the "induced fit" and "multisubstrate recognition". Hirotsu et al. determined three-dimensional structures of various natural composite biocatalysts. Esaki et al. revealed the mechanism of biosynthesis of iron-sulfur clusters and developed a novel process for the production of chiral compounds by the use of novel composite biocatalysts. Shimada et al. showed that incorporation of a chemically modified heme into heme proteins is a powerful tool for the preparation of a highly efficient protein-based catalyst. Kitazume et al. demonstrated that catalytic antibodies exhibit a novel function in ionic liquids.