GALNT13

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. GALNT13 is the 13th member of this enzyme family. This isozyme is highly homologous to GALNT1, however this is specifically expressed in neurons, suggesting the synthesis of neuron specific Tn-antigens.
O-glycan Tn-antigen mucin tumor marker

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