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-acetylgalactosaminyl) to serine and threonine residues of various proteins, thereby initiating mucin-type O-linked glycosylation in the Golgi apparatus. GalNAc-T10 (Polypeptide N-acetylgalactosaminyltransferase 10), also known as UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 10, is a 603 amino acid single-pass type II membrane protein that prefers Muc5Ac and EA2 peptide substrates. 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-T10 is widely expressed, with highest levels found in small intestine. There are four isoforms of GalNAc-T10 that are produced as a result of alternative splicing events.