Hokkaido University · Biochemistry, Genetics and Molecular Biology
Professor Atsuo Kimura's research lab specializes in structural and enzymatic studies of glycoside hydrolases, particularly focusing on α-glucosidases and dextranases. The lab investigates the molecular mechanisms underlying substrate specificity, catalytic mechanisms, and enzyme dynamics using X-ray crystallography, kinetic analysis, and site-directed mutagenesis. Key research directions include understanding the structural basis of long-chain oligosaccharide recognition in enzymes like sugar beet α-glucosidase and the functional roles of conserved domains in dextranase from *Streptococcus mutans*. The lab also explores enzyme inactivation mechanisms using mechanism-based inhibitors such as conduritol B epoxide to identify critical catalytic residues.
Figures are computed from collected data and may differ slightly.
Sugar beet α-glucosidase (SBG), a member of glycoside hydrolase family 31, shows exceptional long-chain specificity, exhibiting higher kcat/Km values for longer malto-oligosaccharides. However, its amino acid sequence is similar to those of other short chain-specific α-glucosidases. To gain structural insights into the long-chain substrate recognition of SBG, a crystal structure complex with the pseudotetrasaccharide acarbose was determined at 1.7 Å resolution. The active site pocket of SBG is f
Dextranase is an enzyme that hydrolyzes dextran α-1,6 linkages. Streptococcus mutans dextranase belongs to glycoside hydrolase family 66, producing isomaltooligosaccharides of various sizes and consisting of at least five amino acid sequence regions. The crystal structure of the conserved fragment from Gln(100) to Ile(732) of S. mutans dextranase, devoid of its N- and C-terminal variable regions, was determined at 1.6 Å resolution and found to contain three structural domains. Domain N possessed
(1992). Complete Amino Acid Sequence of Crystalline (α–Glucosidase from Aspergillus niger. Bioscience, Biotechnology, and Biochemistry: Vol. 56, No. 8, pp. 1368-1370.
α-グルコシダーゼは、植物や動物組織における澱粉・グリコーゲン代謝に関与しており、基質認識が多様性であることが特徴である。最近の研究により、α-グルコシダーゼが2つのグループ(ファミリーIとファミリーII)に大別され、ファミリーIはα-アミーゼファミリーに属することが明かにされた。本稿では、α-グルコシダーゼファミリーの相違に力点を置き、触媒アミノ酸(求核基と酸塩基触媒基)を含む構造情報、基質の分子認識や加水分解反応の遷移状態における中間体について記述する。
The substrate specificity of honeybee alpha-glucosidase I, a monomeric enzyme was kinetically investigated. Unusual kinetic features were observed in the cleavage reactions of sucrose, maltose, p-nitrophenyl alpha-glucoside, phenyl alpha-glucoside, turanose, and maltodextrin (DP = 13). At relatively high substrate concentrations, the velocities of liberation of fructose from sucrose, glucose from maltose, p-nitrophenol from p-nitrophenyl alpha-glucoside, and phenol from phenyl alpha-glucoside we
The catalytic amino acid residue of Aspergillus niger alpha-glucosidase (ANGase) was identified by modification with conduritol B epoxide (CBE), a mechanism-based irreversible inactivator. The inactivation by CBE followed pseudo-first order kinetics. The interaction of CBE and ANGase conformed to a model with a reversible enzyme-inhibitor complex formed before covalent inactivation. A competitive inhibitor, Tris, decreased the inactivation rate. The incorporation of one mole of CBE per mole of A
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