Comparative study of the inhibition of α-glucosidase, α-amylase, and cyclomaltodextrin glucanosyltransferase by acarbose, isoacarbose, and acarviosine-glucose

Bacillus stearothermophilus maltogenic amylase hydrolyzes the first glycosidic linkage of acarbose to give acarviosine-glucose. In the presence of carbohydrate acceptors, acarviosine-glucose is primarily transferred to the C-6 position of the acceptor. When D-glucose is the acceptor, isoacarbose is formed. Acarbose, acarviosine-glucose, and isoacarbose were compared as inhibitors of α-glucosidase, α-amylase, and cyclomaltodextrin glucanosyltransferase. The three inhibitors were found to be competitive inhibitors for α-glucosidase and mixed noncompetitive inhibitors for α- amylase and cyclomaltodextrin glucanosyltransferase. The K(i) values were dependent on the type of enzyme and their source. Acarviosine-glucose was a potent inhibitor for baker's yeast α-glucosidase, inhibiting 430 times more than acarbose, and was an excellent inhibitor for cyclomaltodextrin glucanosyltransferase, inhibiting 6 times more than acarbose. Isoacarbose was the most effective inhibitor of α-amylase and cyclomaltodextrin glucanosyltransferase, inhibiting 15.2 and 2.0 times more than acarbose, respectively.