Polypeptide N-acetylgalactosaminyltransferase 4 (GALNT4)

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 a highest activity toward Muc7, EA2 and Muc2, with a lowest action than GALNT2.

Glycosylates 'Thr-57' of SELPLG. .