The protein encoded by this gene is a member of the sialyltransferase family. Members of this family are enzymes that transfer sialic acid from the activated cytidine 5'-monophospho-N-acetylneuraminic acid to terminal positions on sialylated glycolipids (gangliosides) or to the N- or O-linked sugar chains of glycoproteins. This protein has high specificity for neolactotetraosylceramide and neolactohexaosylceramide as glycolipid substrates and may contribute to the formation of selectin ligands and sialyl Lewis X, a carbohydrate important for cell-to-cell recognition and a blood group antigen. [provided by RefSeq, Apr 2016].