1Q6C

Crystal Structure of Soybean Beta-Amylase Complexed with Maltose

1Q6C の概要

• エントリーDOI: 10.2210/pdb1q6c/pdb
• 関連するPDBエントリー: 1Q6D 1Q6E 1Q6F 1Q6G
• 関連するBIRD辞書のPRD_ID: PRD_900001
• 分子名称: beta-amylase, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, SULFATE ION, ... (4 entities in total)
• 機能のキーワード: beta-alpha-barrels, beta-amylase, maltose complex, hydrolase
• 由来する生物種: Glycine max (soybean)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 56745.83

構造登録者

Hirata, A.,Adachi, M.,Sekine, A.,Kang, Y.N.,Utsumi, S.,Mikami, B. (登録日: 2003-08-13, 公開日: 2004-02-24, 最終更新日: 2024-03-13)

主引用文献

Hirata, A.,Adachi, M.,Sekine, A.,Kang, Y.N.,Utsumi, S.,Mikami, B.
Structural and Enzymatic Analysis of Soybean {beta}-Amylase Mutants with Increased pH Optimum
J.Biol.Chem., 279:7287-7295, 2004

PubMed Abstract: Comparison of the architecture around the active site of soybean beta-amylase and Bacillus cereus beta-amylase showed that the hydrogen bond networks (Glu380-(Lys295-Met51) and Glu380-Asn340-Glu178) in soybean beta-amylase around the base catalytic residue, Glu380, seem to contribute to the lower pH optimum of soybean beta-amylase. To convert the pH optimum of soybean beta-amylase (pH 5.4) to that of the bacterial type enzyme (pH 6.7), three mutants of soybean beta-amylase, M51T, E178Y, and N340T, were constructed such that the hydrogen bond networks were removed by site-directed mutagenesis. The kinetic analysis showed that the pH optimum of all mutants shifted dramatically to a neutral pH (range, from 5.4 to 6.0-6.6). The Km values of the mutants were almost the same as that of soybean beta-amylase except in the case of M51T, while the Vmax values of all mutants were low compared with that of soybean beta-amylase. The crystal structure analysis of the wild type-maltose and mutant-maltose complexes showed that the direct hydrogen bond between Glu380 and Asn340 was completely disrupted in the mutants M51T, E178Y, and N340T. In the case of M51T, the hydrogen bond between Glu380 and Lys295 was also disrupted. These results indicated that the reduced pKa value of Glu380 is stabilized by the hydrogen bond network and is responsible for the lower pH optimum of soybean beta-amylase compared with that of the bacterial beta-amylase.

PubMed: 14638688
DOI: 10.1074/jbc.M309411200

実験手法

X-RAY DIFFRACTION (1.86 Å)