Purification and Substrate Specificity of Honeybee, Apis mellifera L., α-Glucosidase 3

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  • NISHIMOTO Mamoru
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • KUBOTA Masaki
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • TSUJI Masahisa
    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
  • MATSUI Hirokazu
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University
  • CHIBA Seiya
    Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University

書誌事項

タイトル別名
  • Purification and Substrate Specificity of Honeybee, Apis mellifera L., .ALPHA.-Glucosidase III.
  • Purification and Substrate Specificity of Honeybee Apis mellifera L アルファ Glucosidase 3
  • Purification and Substrate Specificity of Honeybee, Apis mellifera L., α-Glucosidase III

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抄録

α-Glucosidase III, which was different in substrate specificity from honeybee α-glucosidases I and II, was purified as an electrophoretically homogeneous protein from honeybees, by salting-out chromatography, DEAE-cellulose, DEAE-Sepharose CL-6B, Bio-Gel P-150, and CM-Toyopearl 650M column chromatographies. The enzyme preparation was confirmed to be a monomeric protein and a glycoprotein containing about 7.4% of carbohydrate. The molecular weight was estimated to approximately 68,000, and the optimum pH was 5.5. The substrate specificity of α-glucosidase III was kinetically investigated. The enzyme did not show unusual kinetics, such as the allosteric behaviors observed in α-glucosidases I and II, which are monomeric proteins. The enzyme was characterized by the ability to rapidly hydrolyze sucrose, phenyl α-glucoside, maltose, and maltotriose, and by extremely high Km for substrates, compared with those of α-glucosidases I and II. Especially, maltotriose was hydrolyzed over 3 times as rapidly as maltose. However, maltooligosaccharides of four or more in the degree of polymerization were slowly degraded. The relative rates of the k0 values for maltose, sucrose, p-nitrophenyl α-glucoside and maltotriose were estimated to be 100, 527, 281 and 364, and the Km values for these substrates, 11, 30, 13, and 10 mM, respectively. The subsite affinities (Ai’s) in the active site were tentatively evaluated from the rate parameters for maltooligosaccharides. In this enzyme, it was peculiar that the Ai value at subsite 3 was larger than that of subsite 1.

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