Catalytic Amino Acid Residue Providing Proton Donor in .ALPHA.-Glucosidase Family II.

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  • Okuyama Masayuki
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • Mori Haruhide
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • Kimura Atsuo
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • Chiba Seiya
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University

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  • FamilyIIに属するα-Glucosidaseのプロトン供与体としての触媒アミノ酸残基
  • Family 2に属するα-Glucosidaseのプロトン供与体としての触媒アミノ酸残基
  • Family 2 ニ ゾクスル アルファ Glucosidase ノ プロトン キョウヨタイ ト シテ ノ ショクバイ アミノサンザンキ

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Abstract

cDNA encoding Schizosaccharomyces pombe a-glucosidase was cloned, and expressed in Saccharomyces cerevisiae. The deduced amino acid sequence categorized under the α-glucosidase family II showed a high homology to those of a-glucosidase from molds, plants and mammals. By site direct mutagenesis, Asp481, G1u484, and Asp647 residues were confirmed to be essential in the catalytic reaction. The carboxyl group (-COON) of the Asp647 residue was for the first time pointed out to be the candidate of proton donor in the a-glucosidase of family II. The carboxylate group (-COO-) of the Asp481 residue was assumed to be the secondary carboxylate group, which stabilize the oxocarbenium ion through electrostatic interaction, and the Asp481 was considered to be modified by the chemical modification with conduritol B epoxide. The role of the G1u484 residue, which was the third residue, was presumed to be to fix the reaction intermediate of substrates.

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