title: Catalytic role of the calcium ion in GH97 inverting glycoside hydrolase.
abstract: The role of calcium ion in the active site of the inverting glycoside hydrolase family 97 enzyme, BtGH97a, was investigated through structural and kinetic studies. The calcium ion was likely directly involved in the catalytic reaction. The pH dependence of kcat/Km values in the presence or absence of calcium ion indicated that the calcium ion lowered the pKa of the base catalyst. The significant decreases in kcat/Km for hydrolysis of substrates with basic leaving groups in the absence of calcium ion confirmed that the calcium ion facilitated the leaving group departure.
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan. Electronic address: okuyama@abs.agr.hokudai.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Okuyama
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan; Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8528, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Hondoh
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Haruhide
authors.initials: H
authors.lastname: Mori
authors.affiliation: Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Kimura
mesh_terms: D055162:Biocatalysis; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020134:Catalytic Domain; D004492:Edetic Acid / Q000737:chemistry; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular
chemical_list: D004492:Edetic Acid; D006026:Glycoside Hydrolases; D002118:Calcium
keywords: Calcium ion dependent glycosidase; Glycoside hydrolase family 97; Kinetic analysis; Structural analysis