添加亲核试剂和pH值对α-D-甘露糖苷酶催化反应的影响。
Effect of added nucleophiles and pH on alpha-D-mannosidase-catalyzed reactions.
作者信息
De Prijcker J, De Bruyne C K
出版信息
Carbohydr Res. 1975 Aug;43(1):173-82. doi: 10.1016/s0008-6215(00)83983-x.
The effect of (1) added nucleophiles, (2) the concentration of water, and (3) pH on the alpha-D-mannosidase-catalyzed hydrolysis of substituted phenyl alpha-D-mannopyranosides has been investigated.. A two-step mechanism, with formation of a mannosyl-enzyme complex, is proposed. With the phenyl alpha-D-mannopyranosides, the formation of this intermediate complex is the rate-limiting step. The activity of the enzyme is controlled by two dissociable groups having pK approximately 3 and pK approximately 6, respectively. It is proposed that one of the groups functions as a proton-donor, whereas the other group stabilizes the mannosyl-enzyme complex by ion-pair formation or covalent binding.
研究了（1）添加亲核试剂、（2）水浓度和（3）pH对α-D-甘露糖苷酶催化取代苯基α-D-甘露吡喃糖苷水解的影响。提出了一个两步机制，其中形成了甘露糖基-酶复合物。对于苯基α-D-甘露吡喃糖苷，这种中间复合物的形成是限速步骤。该酶的活性由两个可解离基团控制，其pK值分别约为3和约为6。有人提出，其中一个基团起质子供体的作用，而另一个基团通过离子对形成或共价结合来稳定甘露糖基-酶复合物。
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