The UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-T) family of enzymes are substrate-specific proteins that catalyze the transfer of GalNAc (N-acetylgalactosamine) to serine and threonine residues onto various proteins, thereby initiating mucin-type O-linked glycosylation in the Golgi apparatus. GalNAc-T11 (Polypeptide N-acetylgalactosaminyltransferase 11), also known as UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 11, is a 608 amino acid protein that catalyzes glycosylation of Muc1, Muc4.1 and EA2, though it does not display enzymatic preference for erythropoitein. The N-terminal domain is involved in substrate binding and manganese coordination, while the C-terminal domain is involved in UDP-Gal binding and catalytic reaction. GalNAc-T11 is highly expressed in kidney tubules, though it is not expressed in glomeruli. There are two isoforms of GalNAc-T11 that are produced as a result of alternative splicing events.