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Catalytic role of the calcium ion in GH97 inverting glycoside hydrolase |
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| Authors: | Masayuki Okuyama Takuya Yoshida Hironori Hondoh Haruhide Mori Min Yao Atsuo Kimura |
| Institution: | 1. Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan;2. Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, Hiroshima 739-8528, Japan;3. Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan |
| 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. |
| Keywords: | BSA bovine serum albumin 2C4NPG 2-chloro-4-nitrophenyl α-d-glucopyranoside 4C2NPG 4-chloro-2-nitrophenyl α-d-glucopyranoside 2 4DNPG 2 4-dinitrophenyl α-d-glucopyranoside 3 4DNPG 3 4-dinitrophenyl α-d-glucopyranoside EDTA ethylenediamine-N N N&prime N&prime -tetraacetic acid GH glycoside hydrolase family MNPG m-nitrophenyl α-d-glucopyranoside PNPG p-nitrophenyl α-d-glucopyranoside |
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