抄録
1. Inhibition by eleven substrate analogues of the hydrolytic reaction of phenyl α-maltoside into phenol and maltose catalyzed by saccharifying α-amylase [EC 3. 2. 1. 1] from B. subtilis*4 (1) was studied at 25°C and at pH 5.4.
2. Types of inhibition and inhibitor constants were determined at a fixed concentration of each analogue by varying the substrate concentration. The analogues showed competitive inhibition, except for β-maltose and eq-maltose (an equilibrium mixture of α- and β-anomers of maltose), which showed noncompetitive inhibition and mixed-type inhibition, respectively. Analysis of the results revealed that α-maltose is a competitive inhibitor.
3. Using eq-D-glucose, methyl α-D-glucoside, and β-maltose as inhibitors, the relationship between the concentration of inhibitor (i) and the reciprocal initial velocity (1/v) was investigated. The plot of 1/v versus i for each analogue was linear and in good agreement with the theoretical line expected from the type of inhibition and inhibitor constant Ki of each analogue as above determined.
4. The results are compared with those obtained for glucoamylase*5 [EC 3. 2. 1. 3] from Rh. delemar and Taka-amylase A*6 [EC 3. 2. 1. 1] reported previously.
