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

Abstract

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 O S 2→B 2,5→1 S 5 and 3 S1 →3 H 4→1 C 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 4 C 1→4 H 5/1 S 5→1 S 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 2,5/1 S 5→1 S 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.