The α-Thioglycoligase Derived from a GH89 α-N -Acetylglucosaminidase Synthesises α-N -Acetylglucosamine-Based Glycosides of Biomedical Interest

We report here on the preparation of a novel a-thioglycoligase that can be used for the fast and efficient synthesis of a-N-acetylglucosaminebased glycosides. Using the a-N-acetyl-glucosaminidase from Clostridium perfringens of family GH89 (according to the Carbohydrate Active Enzymes classification) as starting point, we prepared mutants in the acid/base residue glutamic acid 483 that were found to have different synthetic efficiencies (maximal yields >80% after 24 h) in the presence of an activated donor and suitable acceptors. The synthetic potential of the Glu483 alanine mutant as an a-thioglycoligase – only the third biocatalyst with this stereospecificity reported to date, and the first selective for the N-acetylglucosamine moiety – was demonstrated by producing for the first time N-acetyl-a-dglucosaminyl azide and N-acetylglucosamine a-thioglycosides in high yields. To showcase the application of such compounds, we show that they offer the wild-type CpGH89 protection from thermal unfolding, demonstrating their potential as pharmacological chaperones for the treatment of mucopolysaccharidosis IIIB (Sanfilippo syndrome).