Polypeptide N-acetylgalactosaminyltransferase 12 (GALNT12)

Catalyzes the initial reaction in O-linked oligosaccharide biosynthesis, the transfer of an N-acetyl-D- galactosamine residue to a serine or threonine residue on the protein receptor. Has action toward non-glycosylated peptides like Muc5AC, Muc1a and EA2, and no detectable activity with Muc2 and Muc7.

Displays enzymatic activity toward the Gal-NAc- Muc5AC glycopeptide, but no detectable activity to mono-GalNAc- glycosylated Muc1a, Muc2, Muc7 and EA2. May play an essential role in the initial step of mucin-type oligosaccharide biosynthesis in digestive organs.