Hirayama T, Nagayama H, Matsuda K
J Biochem. 1980 Apr;87(4):1203-8.
Kinetic studies of the two beta-glucosidase isozymes, GB-1 and GB-2, which were from the culture filtrate of a phytopathogenic fungus Pyricularia oryzae, revaled that the latter isozyme was an allosteric protein with two substrate binding sites. The homotropic effects of o- and m-nitrophenyl-beta-D-glucosides on GB-2 showed positive cooperativity, whereas that of cell cellooligosaccharide showed negative cooperatively. The affinity of GB-2 for cellooligosaccharide tended to increase with decreasing chain length, in contrast to that of GB-1. Glucono-delta-lactone and glucose acted as competitive inhibitors of GB-1 and GB-2. As regards the control of the level of glucose formed by the cellulose system, it appears that the rate of formation of glucose by beta-glucosidase is reduced by the presence of the substrate, cellooligosaccharide, as well as by the product, glucose.
对来自植物病原真菌稻瘟病菌培养滤液中的两种β-葡萄糖苷酶同工酶GB-1和GB-2的动力学研究表明，后一种同工酶是一种具有两个底物结合位点的别构蛋白。邻硝基苯基-β-D-葡萄糖苷和间硝基苯基-β-D-葡萄糖苷对GB-2的同促效应表现为正协同性，而纤维寡糖的同促效应则表现为负协同性。与GB-1相反，GB-2对纤维寡糖的亲和力倾向于随着链长的缩短而增加。葡萄糖酸-δ-内酯和葡萄糖作为GB-1和GB-2的竞争性抑制剂。关于纤维素系统形成葡萄糖水平的控制，似乎β-葡萄糖苷酶形成葡萄糖的速率会因底物纤维寡糖以及产物葡萄糖的存在而降低。
