GALNT12 is a member of a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (EC 2.4.1.41), which catalyze the transfer of N-acetylgalactosamine (GalNAc) from UDP-GalNAc to a hydroxyl amino acid on a polypeptide acceptor in the initial step of mucin-type O-linked protein glycosylation (Guo et al., 2002 [PubMed 12135769]).[supplied by OMIM