Beta-galactosyl-N-acetylglucosaminylgalactosylglucosyl-ceramide beta-1,3-acetylglucosaminyltransferase (, uridine diphosphoacetylglucosamine-acetyllactosaminide beta1->3-acetylglucosaminyltransferase, poly-N-acetyllactosamine extension enzyme, UDP-N-acetyl-D-glucosamine:beta-D-galactosyl-1,4-N-acetyl-beta-D-glucosaminyl-1,3-beta-D-galactosyl-1,4-beta-D-glucosylceramide beta-1,3-acetylglucosaminyltransferase) is an enzyme with systematic name UDP-N-acetyl-D-glucosamine:beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosaminyl-(1->3)-beta-D-galactosyl-(1->4)-beta-D-glucosyl-(1<->1)-ceramide 3-beta-N-acetylglucosaminyltransferase. This enzyme catalyses the following chemical reaction
This enzyme requires Mn<sup>2+</sup>.