acetylglucosaminyltransferase activity beta-1,3-galactosyl-O-glycosyl-glycoprotein beta-1,3-N-acetylglucosaminyltransferase activity https://github.com/geneontology/go-ontology/issues/30193 molecular_function Catalysis of the reaction: beta-D-galactosyl-1,3-(N-acetyl-D-glucosaminyl-1,6)-N-acetyl-D-galactosaminyl-R + UDP-N-acetyl-D-glucosamine = N-acetyl-beta-D-glucosaminyl-1,3-beta-D-galactosyl-1,3-(N-acetyl-beta-D-glucosaminyl-1,6)-N-acetyl-D-galactosaminyl-R + UDP. EC:2.4.1.146 O-glycosyl-oligosaccharide-glycoprotein N-acetylglucosaminyltransferase II activity UDP-N-acetyl-D-glucosamine:O-glycosyl-glycoprotein (N-acetyl-D-glucosamine to -D-galactose of beta-D-galactosyl-1,3-(N-acetyl-D-glucosaminyl-1,6)-N-acetyl-D-galactosaminyl-R) beta-1,3-N-acetyl-D-glucosaminyltransferase activity elongation 3-beta-GalNAc-transferase activity Reactome:R-HSA-5617096 MetaCyc:2.4.1.146-RXN GO:0047223 uridine diphosphoacetylglucosamine-mucin beta(1->3)-acetylglucosaminyltransferase (elongating) elongation 3beta-GalNAc-transferase activity catalytic activity, acting on a glycoprotein