ST3Gal-I was originally purified from porcine liver, and the amino acid sequences derived were used for polymerase chain reaction (PCR)-directed cDNA cloning (Gillespie et al. 1992). ST3Gal-I is at present one of six members of the α2,3- sialyltransferase gene family (Ishii et al. 1993; Tsuji et al. 1996; Okajima et al. 1999), and one of the few sialyltransferases that have relatively strict acceptor specificity. Only the corel O-glycan Galβ1→3GalNAc→Ser/Thr can be utilized by ST3Gal-I as an acceptor. The resulting oligosaccharide product is a sialylated corel O-glycan with the structure NeuAcα2→3Galβ1→3GalNAcα1→Ser/Thr, which may also be further sialylated by certain α2,6-sialyltransferases, resulting in a fully sialylated tetrasaccharide: NeuAα2→3Galβ1→3(NeuAα2→6)GalNAcα1→Thr/Ser.
KeywordsSialic Acid Porcine Liver Peanut Agglutinin Medullary Thymocyte Human Thymic Epithelial Cell
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