α-アミラーゼー基質複合体の結晶構造と触媒機構モデル
2000 年 42 巻 2 号 p. 165-170
詳細
2000 年 42 巻 2 号 p. 165-170
X-ray crystal structure of a catalytic-site mutant EQ208 [Glu2O8→Gln] of α-amylase from Bacillus subtilis complexed with maltopentaose (G5) has been determined at 2.5 Å resolution. The conformation around the third α- (1, 4) -glucosidic bond makes a sharp turn, allowing the substrate to fit into the L-shaped cleft of the active site. The amide nitrogen of G1n208 forms a hydrogen bond with the glucosidic oxygen in the scissile bond. The carboxyl group of Asp 176 has non-bonded contacts to the anomeric carbon atom and to the endocyclic oxygen atom. Thus, G1u208 may act as a proton donor and Asp176 may stabilize the oxocarbonium ion at the catalysis.
