preferred_name: N-acetyl-alpha-D-galactosaminyl-di-trans,octa-cis-undecaprenyl diphosphate + UDP-N-acetyl-alpha-D-galactosamine => alpha-D-GalNAc-(1->3)-alpha-D-GalNAc-di-trans,octa-cis-undecaprenyl diphosphate + UDP + H(+)