ST3 Beta-Galactoside Alpha-2,3-Sialyltransferase 1 (ST3GAL1)

Abstract

Sialyltransferases which add sialic acid with α2,3-, α2,6-, or α2,8-linkages contribute to the terminal of carbohydrate structures and functions of cell surface molecules including glycolipids and glycoproteins (Tsuji et al. 1996; Harduin-Lepers et al. 2001; Audry et al. 2011). Glycans with α2,3-linked sialic acids present on cell surface are known as receptors of viruses such as influenza viruses and target molecules of siglecs, which contain an immunoglobulin domain with lectin activity capturing sialic acids. So far, there are six α2,3-sialyltransferases in mammal genome. The first cDNA of ST3GAL1 was cloned based on the deduced peptide sequences of purified α2,3-sialyltransferase from porcine liver (Gillespie et al. 1992), and orthologues have been found in many vertebrate genomes. Since ST3GAL1 has a strict acceptor specificity toward type III glycans (Galβ1→3GalNAc), ST3GAL1 predominantly adds sialic acid to the core 1 O-glycan, Galβ1→3GalNAc→Ser/Thr, which is a major core structure of mucin-type O-glycans. For instance, the resulting oligosaccharide product is a sialylated core 1 O-glycan, NeuAcα2→3Galβ1→3GalNAc→Ser/Thr, which is also further sialylated by certain α2,6-sialyltransferases, generating a fully sialylated tetrasaccharide: NeuAcα2→3Galβ1→3(NeuAcα2→6)GalNAc→Ser/Thr (Fig. 57.1).