Alpha-1,6-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase (, N-acetylglucosaminyltransferase VI, N-glycosyl-oligosaccharide-glycoprotein N-acetylglucosaminyltransferase VI, uridine diphosphoacetylglucosamine-glycopeptide beta-1->4-acetylglucosaminyltransferase VI, mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase, GnTVI) is an enzyme with systematic name UDP-N-acetyl-D-glucosamine:2,6-bis(N-acetyl-beta-D-glucosaminyl)-alpha-D-mannosyl-glycoprotein 4-beta-N-acetyl-D-glucosaminyltransferase. This enzyme catalyses the following chemical reaction
R represents the remainder of the N-linked oligosaccharide in the glycoprotein acceptor.