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 the same enzyme activity toward Muc1, Muc4.1, and EA2 than GALNT1. Does not appear to be involved in glycosylation of erythropoietin.
Highly expressed in kidney. Expressed at intermediate level in brain, heart and skeletal muscle. Weakly expressed other tissues. In kidney, it is strongly expressed in tubules but not expressed in glomeruli.
Protein modification; protein glycosylation.
Belongs to the glycosyltransferase 2 family. GalNAc-T subfamily. Contains 1 ricin B-type lectin domain.
There are two conserved domains in the glycosyltransferase region: the N-terminal domain (domain A, also called GT1 motif), which is probably involved in manganese coordination and substrate binding and the C-terminal domain (domain B, also called Gal/GalNAc-T motif), which is probably involved in catalytic reaction and UDP-Gal binding. The ricin B-type lectin domain binds to GalNAc and contributes to the glycopeptide specificity.