The function of ENSG00000136542 (GALNT5, polypeptide N-acetylgalactosaminyltransferase 5) is as follows. 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 EA2 peptide substrate, but has a weak activity toward Muc2 or Muc1b substrates (By similarity). .