北海道大学 · 生化学・遺伝学・分子生物学
Kimura教授の研究室は、炭水化物代謝に関与する糖達生成酵素の構造・機能解明を柱としており、特にα-グルコシダーゼの基質特異性と触媒機構に焦点を当てた構造生物学的研究を展開しています。糖鎖の認識機構を解明するため、結晶構造解析やキネティクス解析を駆使し、長鎖マルトオリゴサッカライドを特異的に認識する酵素の立体構造的特徴を解明しています。また、酵素阻害剤を用いたアミノ酸残基の同定や、反応遷移状態の解明にも取り組んでいます。
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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