GALNT1

HO-Ser/Thr-protein		GalNAc(alpha-1-O)-Ser/Thr-protein

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 known as a tumor marker, which is the base structure of mucin type O-glycan. The acceptor substrate (protein) is typically Mucin. GALNT1 is the first member of this enzyme family. In general, this isozyme exhibits strong activities toward typical mucin-box-peptide, as has been used a standard of this family. The first crystal structure of the GALNT family was determined by useing this isozyme (Fritz et al. 2004), and thus it is also used as a standerd in structure-function relationship analysis.
O-glycan Tn-antigen mucin tumor marker

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