Kinetics studies on the inhibition mechanism of pancreatic α-amylase by glycoconjugated 1H-1,2,3-triazoles: a new class of inhibitors with hypoglycemiant activity.

Glycoconjugated 1H-1,2,3-triazoles (GCTs) comprise a new class of glycosidase inhibitors that are under investigation as promising therapeutic agents for a variety of diseases, including type 2 diabetes mellitus. However, few kinetics studies have been performed to clarify the mode of inhibition of GCTs with their target glycosidases. Our group has previously shown that some methyl-β-D-ribofuranosyl-1H-1,2,3-triazoles that inhibit baker's yeast maltase were also able to reduce post-prandial glucose levels in normal rats. We hypothesized that this hypoglycemiant activity was attributable to inhibition of mammalian α-glucosidases involved in sugar metabolism, such as pancreatic α-amylase. Hence, the aim of this work was to test a series of 26 GCTs on porcine pancreatic α-amylase (PPA) and to characterize their inhibition mechanisms. Six GCTs, all ribofuranosyl-derived GCTs, significantly inhibited PPA, with IC(50) values in the middle to high micromolar range. Our results also demonstrated that ribofuranosyl-derived GCTs are reversible, noncompetitive inhibitors when using 2-chloro-4-nitrophenyl-α-D-maltotrioside as a substrate. E/ES affinity ratios (α) ranged from 0.3 to 1.1, with the majority of ribofuranosyl-derived GCTs preferentially forming stable ternary ESI complexes. Competition assays with acarbose showed that ribofuranosyl-derived GCTs bind to PPA in a mutually exclusive fashion. The data presented here show that pancreatic α-amylase is one of the possible molecular targets in the pharmacological activity of ribofuranosyl-derived GCTs. Our results also provide important mechanistic insight that can be of major help to develop this new class of synthetic small molecules into more potent compounds with anti-diabetic activity through rational drug design.