α-N-Acetylglucosaminidase from Bifidobacterium bifidum specifically hydrolyzes α-linked N-acetylglucosamine at nonreducing terminus of O-glycan on gastric mucin.

α-Linked N-acetylglucosamine is one of the major glyco-epitopes in O-glycan of gastroduodenal mucin. Here, we identified glycoside hydrolase (GH) family 89 α-N-acetylglucosaminidase, termed AgnB, from Bifidobacterium bifidum JCM 1254, which is essentially specific to GlcNAcα1-4Gal structure. AgnB is a membrane-anchored extracellular enzyme consisting of a GH89 domain and four carbohydrate-binding module (CBM) 32 domains.