Reaction catalyzed by polypeptide N-acetylgalactosaminyltransferase (2.4.1.41)
+
=
GalNAc-Thr3-MUC5AC-13
+
MUC5AC-13
+
UDP-GalNAc
=
GalNAc-Thr3-MUC5AC-13
+
UDP