【摘要】 比较了猕猴桃蛋白酶（Actinidin）在盐酸胍中变性时的荧光变化与活力变化的关系。当胍浓度为0.1 mol/l时,酶的最大荧光发射波长λ_max不变,荧光强度上升。此时酶被激活,活力提高25％,激活速度比变性速度快5.0倍。胍浓度逐渐增大,酶λ_max略红移,4.0 mol/l时达336 nm。但荧光强度降低,酶表现为快相和慢相失活的二个一级反应,失活速度常数比变性速度常数快 1～3个数量级。Actinidin 的激活与失活现象显示这可能与活性部位相关的 Trp 微环境的构象变化有关。胍变性结果指出 Actinidin 构象变化速度小于活力变化速度,这代表酶变性反应时慢构象变化快活力变化的一种模式。更多还原

【Abstract】 The denaturation rate and inactivation/activation rate of actinidin in guanidine hy-drochloride solution <Gdn) had been studied. Though the maximum fluorescence emission wave length (λmax) remained constand, fluorescence intensity of buffered actinidin increased with the addition of 0. 1 mol/1 Gdn. The enzyme relative activity was increased by 25% and the rate of activation was five times greater than that of denaturation. As guanidine concentration increased from 0. 3 to 4. 0 mol/l, λmax was red-shifted from 331 to 336 nm, but the fluorescence intensity was reduced. The enzyme inactivation was a combination of two simple first-order reactions (fast-phase and slow-phase) in the presence of higher concentrations of Gdn. It is demonstrated that the changes of actinidin activity may be connected with the changes of the enzyme conformation with the micro-environment of trypto-phan. The changes of the micro-environment may activate or inhibit the activity. Furthermore, actinidin denaturation by higher concentration of guanidine indicates that the denaturation rates of actinidin are slower than the inactivation rates of the enzyme. This is one of the three models suggested on the relationship between conformation and activity of enzymes.更多还原