GO:0004653

polypeptide N-acetylgalactosaminyltransferase activity

Details: 
Catalysis of the reaction: UDP-N-acetyl-D-galactosamine + polypeptide = UDP + N-acetyl-D-galactosaminyl-polypeptide. This reaction is the modification of serine or threonine residues in polypeptide chains by the transfer of a N-acetylgalactose from UDP-N-acetylgalactose to the hydroxyl group of the amino acid; it is the first step in O-glycan biosynthesis. [EC:2.4.1.41, ISBN:0879695595]
Evidence Code: