Tanaka A
Department of Chemistry, Faculty of Education, Mie University, Japan.
Biosci Biotechnol Biochem. 1996 Dec;60(12):2055-8. doi: 10.1271/bbb.60.2055.
Binding equilibria of Aspergillus niger glucoamylase with its several ligands were observed to analyze the binding modes of the ligands. Steady-state kinetic studies using p-nitrophenyl alpha-glucoside as a substrate showed that 1-deoxynojirimycin, which is a mixed type inhibitor for Rhizopus glucoamylase, was a competitive type inhibitor bound at the active site of the enzyme, but gluconolactone, which is also a mixed type inhibitor for Rhizopus glucoamylase, was a non-competitive type inhibitor forming a nonproductive ternary complex with the enzyme and the substrate. beta-Cyclodextrin, which binds to the starch-binding domain of the enzyme, did not inhibit the enzyme activity, showing that there was no interaction between the catalytic domain and the starch-binding domain for the binding of the substrate and beta-cyclodextrin. Isothermal titration calorimetry showed that one 1-deoxynojirimycin molecule and two beta-cyclodextrin molecules bind to the catalytic domain and the starch-binding domain of the enzyme, respectively, and there is no significant interaction between the binding of these ligands.
通过观察黑曲霉葡萄糖淀粉酶与其多种配体的结合平衡来分析配体的结合模式。以对硝基苯基α-葡萄糖苷为底物进行的稳态动力学研究表明，对根霉葡萄糖淀粉酶为混合型抑制剂的1-脱氧野尻霉素是一种结合在酶活性位点的竞争性抑制剂，而同样对根霉葡萄糖淀粉酶为混合型抑制剂的葡萄糖酸内酯是一种与酶和底物形成无活性三元复合物的非竞争性抑制剂。与酶的淀粉结合结构域结合的β-环糊精不抑制酶活性，这表明催化结构域与淀粉结合结构域之间不存在影响底物和β-环糊精结合的相互作用。等温滴定量热法表明，一个1-脱氧野尻霉素分子和两个β-环糊精分子分别与酶的催化结构域和淀粉结合结构域结合，并且这些配体的结合之间不存在显著相互作用。
