In enzymology, a polypeptide N-acetylgalactosaminyltransferase (EC 2.4.1.41) is an enzyme that catalyzes the chemical reaction In enzymology, a polypeptide N-acetylgalactosaminyltransferase (EC 2.4.1.41) is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are UDP-N-acetyl-D-galactosamine and polypeptide, whereas its two products are UDP and N-acetyl-D-galactosaminyl-polypeptide. This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. This enzyme participates in o-glycan biosynthesis and glycan structures - biosynthesis 1. It has 2 cofactors: manganese, and calcium. The systematic name of this enzyme class is UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyl-transferase. Other names in common use include: