GalNAc-T3, soluble fragment, Human Recombinant

Polypeptide N-acetylgalactosaminyltransferase 3 (GalNAc-T3) catalyzes the transfer of N-acetylgalactosamine (GalNAc) from UDP-GalNAc to the hydroxyl group of serine and threonine residues. Twenty GalNAc-T genes have been identified in humans and most have been shown to represent active GalNAc-Ts. All isoforms are type II transmembrane proteins, with different but partly overlapping substrate preferences. The GalNAc-Ts control the initiation of mucin-type O-linked glycosylation and determine the location and density of O-glycans in a protein. Addition of GalNAc to an unglycosylated Ser/Thr residue creates the Tn antigen GalNAcα1-S/T, and subsequent addition of sialic acid by ST6GalNAc-I forms the cancer associated STn antigen. GalNAc-T3 is highly expressed in pancreas and testis, and weakly expressed in a few other organs such as placenta. The expression levels of GalNAc-T3 were found to be upregulated in highly differentiated types of adenocarcinoma cell lines as opposed to less differentiated types. Overexpression of GalNAc-T3 has also been found to promote pancreatic cancer cell growth. Mutations in GalNAc-T3 were found to be involved in familial tumoral calcinosis, which may be mediated through glycosylation of fibroblast growth factor 23, protecting it from proteolytic cleavage. GalNAc-T3 has a preference for mono- or diglycosylated substrates.