Inhibition of β-glycosidases by acarbose analogues containing cellobiose and lactose structures

Acarbose analogues, containing cellobiose and lactose structures, were prepared by reaction of the two disaccharides with acarbose and Bacillus stearothermophilus maltogenic amylase. The kinetics for the inhibition by the two analogues was studied for β-glucosidase, β-galactosidase, cyclomaltodextrin glucanosyltransferase (CGTase), and α-glucosidase. Both analogues were potent competitive inhibitors for β-glucosidase, with K_I values in the range of 0.04-2.44 μM, and the lactose analogues were good uncompetitive inhibitors for β-galactosidase, with K_I values in the range of 159-415 μM, while acarbose was not an inhibitor for either enzyme at 10 and 5 mM, respectively. Both analogues were also potent mixed inhibitors for CGTase, with K_I values in the range of 0.1-9.3 μM. The lactose analogue was a 6.4-fold better competitive inhibitor for α-glucosidase than was acarbose.