a beta-D-GlcNAc-(1->3)-beta-D-Man-(1->4)-beta-D-Glc-(1<->1)-ceramide + UDP-N-acetyl-alpha-D-galactosamine = a beta-D-GalNAc-(1->4)-beta-D-GlcNAc-(1->3)-beta-D-Man-(1->4)-beta-D-Glc-(1<->1)-Cer + UDP + H(+) — reaction