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 Ki values were dependent on the type of enzyme and their source. Acarviosine–glucose was a potent inhibitor for bakerʹs 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.