Details:
Catalysis of the reaction: UDP-N-acetyl-D-galactosamine + alpha-D-galactosyl-(1->4)-beta-D-galactosyl-(1->4)-beta-D-glucosylceramide = UDP + beta-N-acetyl-D-galactosaminyl-(1->3)-alpha-D-galactosyl-(1->4)-beta-D-galactosyl-(1->4)-beta-D-glucosylceramide. [EC:2.4.1.79, MetaCyc:2.4.1.79-RXN]