| Research Abstract |
α-Glucosidase (EC 3.2.1.20), an exo-type glycosidase releasing α-glucose from substrate, is divided into two types of groups (family I and family II) that have different structures and substrate recognition. There are also the glycosidases, of which structures are homologous to each of family enzyme, such as α-amylase for family I and α-xylosidase for family II. The purpose of the project is to investigate the relationship of structure and function of two α-glucosidase families, and to understand the molecular mechanism of glycosidases. 1)The catalytic amino acid residues of two family enzymes were identified. Their functions were also analyzed. 2)The amino acids recognizing the glycon and aglycon moieties of substrate were identified. Two α-glucosidase groups showed the different recognition against the hydroxyl group in the glycon. 3)The crystal of enzyme was prepared. 4)The α-secondary kinetic isotope effects were observed, suggesting the formation of oxo-carbenium ion intermediate in the catalytic reaction. 5)The molecular analysis succeeded in elucidating the function and structure of two α-glucosidase families, and the findings are important to reveal the molecular mechanism of glycosidases homologous to family enzymes.
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