Unlocking the Hydrolytic Mechanism of GH92 α-1,2-Mannosidases: Computation Inspires the use of C-Glycosides as Michaelis Complex Mimics

The conformational changes in a sugar moiety along the hydrolytic pathway are key to understand the mechanism of glycoside hydrolases (GHs) and to design new inhibitors. The two predominant itineraries for mannosidases go via S-O(2)-> B-2,B-5 -> S-1(5) and S-3(1)-> H-3(4)-> C-1(4). For the CAZy family 92, the conformational itinerary was unknown. Published complexes of Bacteroides thetaiotaomicron GH92 catalyst with a S-glycoside and mannoimidazole indicate a C-4(1)-> H-4(5)/S-1(5)-> S-1(5) mechanism. However, as observed with the GH125 family, S-glycosides may not act always as good mimics of GH's natural substrate. Here we present a cooperative study between computations and experiments where our results predict the E-5 -> B-2,B-5/S-1(5)-> S-1(5) pathway for GH92 enzymes. Furthermore, we demonstrate the Michaelis complex mimicry of a new kind of C-disaccharides, whose biochemical applicability was still a chimera.

Automated summary

Understanding the conformational changes in sugar moieties is important for studying glycoside hydrolase mechanisms and designing inhibitors. In this study, the conformational pathway of GH92 enzymes was predicted using computational methods and confirmed with experiments. The study also demonstrated the potential of a new type of C-disaccharides for biochemical applications.