Enzymatic synthesis of a selective inhibitor for α-glucosidases:: α-Acarviosinyl-(1→9)-3-α-D-glucopyranosylpropen

Here, we describe the enzymatic synthesis of novel inhibitors using acarviosine-glucose, as a donor and 3-alpha-D-glucopyranosylpropen (alpha GP) as an acceptor. Maltogenic amylase from Thermus sp. (ThMA) catalyzed the transglycosylation of the acarviosine moiety to alpha GP. The two major reaction products were isolated using chromatographies. Structural analyses revealed that acarviosine was transferred to either C-7 or C-9 of the alpha GP, which correspond to C-4 and C-6 of glucose. Both inhibited rat intestine (x-glucosidase competitively but displayed a mixed-type inhibition mode against human pancreatic alpha-amylase. The alpha-acarviosinyl-(1 -> 7)-3-alpha-D-glucopyranosylpropen showed weaker inhibition potency than acarbose against both alpha-glycosidases. In contrast, the alpha-acarviosinyl-(1 -> 9)-3-alpha-D-glucopyranosylpropen exhibited a 3.0-fold improved inhibition potency against rat intestine a-glucosidase with 0.3-fold inhibition potency against human pancreatic a-amylase relative to acarbose. In conclusion, alpha-acarviosinyl-(1 -> 9)-3-alpha-D-glucopyranosylpropen is a novel alpha-glucosidase-selective inhibitor with 10-fold enhanced selectivity toward alpha-glucosidase over alpha-amylase relative to acarbose, and it could be applied as a potent hypoglycemic agent.