O-GlcNAcase catalyzes the removal of N-acetylglucosamine residues from serine and threonine residues of post-translationally modified proteins using a catalytic mechanism involving substrate-assisted catalysis and general acid/base catalysis. Since thioglycosides are widely perceived as resistant to hydrolysis by glycosidases, it was surprising to find that O-GlcNAcase also catalyzes the efficient hydrolysis of S-glycosides. Brønsted analyses ...