Chiba S
Department of Applied Bioscience, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Biosci Biotechnol Biochem. 1997 Aug;61(8):1233-9. doi: 10.1271/bbb.61.1233.
The hydrolysis of glucosidic linkage catalyzed by every carbohydrate-hydrolase is a reaction in which the product retains (alpha-->alpha or beta-->beta) or inverts (alpha-->beta or beta-->alpha) the anomeric configuration of the substrate. alpha-Glucosidase and glucoamylase are essentially distinguished by releasing alpha-glucose and beta-glucose, respectively, from the common substrates having alpha-glucosidic linkage. The distinction in the substrate specificities of the two enzymes was explained by the subsite affinities in their active sites. The amino acid sequences of the regions containing the catalytic sites were compared in alpha-glucosidases and glucoamylases from various sources. alpha-Glucosidases were suggested to be grouped into two families by their primary structures. The catalytic reaction mechanisms of carbohydrate-hydrolases were discussed in the two significant models of a nucleophilic displacement mechanism and an oxocarbenium ion intermediate mechanism.
每种碳水化合物水解酶催化的糖苷键水解反应中，产物会保留（α→α或β→β）或翻转（α→β或β→α）底物的异头构型。α-葡萄糖苷酶和葡糖淀粉酶的主要区别在于，它们分别从具有α-糖苷键的常见底物中释放出α-葡萄糖和β-葡萄糖。这两种酶底物特异性的差异是由其活性位点中的亚位点亲和力来解释的。对来自不同来源的α-葡萄糖苷酶和葡糖淀粉酶中包含催化位点区域的氨基酸序列进行了比较。α-葡萄糖苷酶根据其一级结构被分为两个家族。碳水化合物水解酶的催化反应机制在亲核取代机制和氧鎓离子中间体机制这两种重要模型中进行了讨论。
