Inhibition of GlcNAc-Processing Glycosidases by C-6-Azido-NAG-Thiazoline and Its Derivatives

NAG-thiazoline is a strong competitive inhibitor of GH20 beta-N-acetylhexosaminidases and GH84 beta-N-acetylglucosaminidases. Here, we focused on the design, synthesis and inhibition potency of a series of new derivatives of NAG-thiazoline modified at the C-6 position. Dimerization of NAG-thiazoline via C-6 attached triazole linkers prepared by click chemistry was employed to make use of multivalency in the inhibition. Novel compounds were tested as potential inhibitors of beta-N-acetylhexosaminidases from Talaromyces flavus, Streptomyces plicatus (both GH20) and beta-N-acetylglucosaminidases from Bacteroides thetaiotaomicron and humans (both GH84). From the set of newly prepared NAG-thiazoline derivatives, only C-6-azido-NAG-thiazoline displayed inhibition activity towards these enzymes; C-6 triazole-substituted NAG-thiazolines lacked inhibition activity against the enzymes used. Docking of C-6-azido-NAG-thiazoline into the active site of the tested enzymes was performed. Moreover, a stability study with GlcNActhiazoline confirmed its decomposition at pH < 6 yielding 2-acetamido-2-deoxy-1-thio-alpha/beta-D-glucopyranoses, which presumably dimerize oxidatively into S-S linked dimers; decomposition products of NAG-thiazoline are void of inhibitory activity.