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 activity toward HIV envelope glycoprotein gp120, EA2, MUC2, MUC1A and MUC5AC (, ). Probably glycosylates fibronectin in vivo . Glycosylates FGF23 (, ).
Subcellular locations: Golgi apparatus, Golgi stack membrane
Resides preferentially in the trans and medial parts of the Golgi stack.
Expressed in organs that contain secretory epithelial glands. Highly expressed in pancreas, skin, kidney and testis. Weakly expressed in prostate, ovary, intestine and colon. Also expressed in placenta and lung and fetal lung and fetal kidney.