Study of the inhibition of four alpha amylases by acarbose and its 4IV-α-maltohexaosyl and 4IV-α-maltododecaosyl analogues

Acarbose analogues, 4(IV)-maltohexaosyl acarbose (G(6)-Aca) and 4(IV)-maltododecaosyl acarbose (G(12)-Aca), were prepared by the reaction of cyclomaltodextrin glucanyltransferase with cyclomaltohexaose and acarbose. The inhibition kinetics of acarbose and the two acarbose analogues were studied for four different alpha-amylases: Aspergillus oryzae, Bacillus amyloliquefaciens, human salivary. and porcine pancreatic alpha-amylases. The three inhibitors showed mixed, noncompetitive inhibition, for all four alpha-amylases. The acarbose inhibition constants, K-i, for the four alpha-amylases were 270, 13, 1.27, and 0.80 muM respectively the K-i values for G(6)-Aca were 33, 37, 14, and 7 nM, respectively; and the G(12)-Aca K-i constants were 59, 81, 18, and 11 nM, respectively. The G(6)-Aca and G(12)-Aca analogues are the most potent a-amylase inhibitors observed, with K-i values one to three orders of magnitude more potent than acarbose, which itself was one to three orders of magnitude more potent than other known alpha-amylase inhibitors. (C) 2003 Elsevier Ltd. All rights reserved.