GALNT3

HO-Ser/Thr		GalNAc(alpha1-O)-Ser/Thr

This enzyme catalyzes the GalNAc-transfer from UDP-GalNAc to Ser or Thr residue in the protein. The product is GalNAc-alpha-O-Ser/Thr structure, so-called Tn-antigen, which is the base structure of mucin type O-glycan. The acceptor substrate (protein) is typically Mucin. GALNT3 is the third member of this enzyme family. In general, this isozyme exhibits strong activities toward continuous S/T sequence, producing the triplet Tn-structure.
O-glycan Tn-antigen mucin tumor marker

Glc	Man	Gal	GlcNAc	GalNAc	Fuc	Xyl	Neu5Ac	Neu5Gc	GlcA	IdoA	GlcN