Glycomonomeric and Glycopolymeric Inhibitors for β-Glucuronidase. π–π Stacking Interaction, Polymeric Effect, and Plausible Conformation

Abstract

N-p-Vinylbenzyl-6-d-glucaramic acid (VB-6-d-GlcaH, 1) and its corresponding polymer, P(VB-6-d-GlcaH-co-AAm) (2), were found to inhibit β-glucuronidase activity more efficiently than d-glucaro-6,3-lactone, while the inhibition ability of N-butyl-6-d-glucaramic acid (Butyl-6-d-GlcaH, 3) on the enzyme activity was seriously lower than that of the lactone. The π–π stacking interaction between the styryl part of 1 and Trp587 of β-glucuronidase was confirmed by the blue shift detected on fluorescence spectrophotometry and the observation of the 3D motif for the active site with the glycomonomer, which must enhance the inhibition ability of the enzyme. In the case of 2, however, such a shift was not observed, which indicated that the effective inhibition of 2 was induced not by the π–π stacking interaction but a polymeric effect. Based on these results and our previous work, plausible conformations of 1 and 2 fitting in β-glucuronidase were proposed.