A GH89 human α-N-acetylglucosaminidase (hNAGLU) homologue from gut microbe Bacteroides thetaiotaomicron capable of hydrolyzing heparosan oligosaccharides

Carbohydrate-Active enZYme (CAZY) GH89 family enzymes catalyze the cleavage of terminal α- N -acetylglucosamine from glycans and glycoconjugates. Although structurally and mechanistically similar to the human lysosomal α- N -acetylglucosaminidase (hNAGLU) in GH89 which is involved in the degradation of heparan sulfate in the lysosome, the reported bacterial GH89 enzymes characterized so far have no or low activity toward α- N -acetylglucosamine-terminated heparosan oligosaccharides, the preferred substrates of hNAGLU. We cloned and expressed several soluble and active recombinant bacterial GH89 enzymes in Escherichia coli . Among these enzymes, a truncated recombinant α- N -acetylglucosaminidase from gut symbiotic bacterium Bacteroides thetaiotaomicron ∆22Bt3590 was found to catalyze the cleavage of the terminal α1–4-linked N -acetylglucosamine (GlcNAc) from a heparosan disaccharide with high efficiency. Heparosan oligosaccharides with lengths up to decasaccharide were also suitable substrates. This bacterial α- N -acetylglucosaminidase could be a useful catalyst for heparan sulfate analysis.