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. Displays activity toward mucin-derived peptide substrates such as Muc2, Muc5AC, Muc7, and Muc13 (-58). May be involved in O-glycosylation in kidney.
Subcellular locations: Golgi apparatus membrane
Detected in renal tubules (at protein level). Highly expressed in fetal and adult kidney. Widely expressed at low level. Weakly expressed in whole brain, cerebellum, thymus, lung, mammary gland, liver, stomach, small intestine, colon, pancreas, spleen, bladder, uterus, placenta, testis, ovary, skeletal muscle, leukocyte, B-cell, bone marrow, fetal brain, fetal thymus, fetal lung, fetal liver, fetal small intestine, fetal spleen, fetal skeletal and fetus. Detected in renal tubules (at protein level).