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In enzymology, a lactosylceramide alpha-2,3-sialyltransferase (EC 2.4.99.9) is an enzyme that catalyzes the chemical reaction

CMP-N-acetylneuraminate + beta-D-galactosyl-1,4-beta-D-glucosylceramide ${\displaystyle \rightleftharpoons }$ CMP + alpha-N-acetylneuraminyl-2,3-beta-D-galactosyl-1,4-beta-D- glucosylceramide

Thus, the two substrates of this enzyme are CMP-N-acetylneuraminate and beta-D-galactosyl-1,4-beta-D-glucosylceramide, whereas its 3 products are CMP, alpha-N-acetylneuraminyl-2,3-beta-D-galactosyl-1,4-beta-D-, and glucosylceramide.

This enzyme belongs to the family of transferases, specifically those glycosyltransferases that do not transfer hexosyl or pentosyl groups. The systematic name of this enzyme class is CMP-N-acetylneuraminate:lactosylceramide alpha-2,3-N-acetylneuraminyltransferase. Other names in common use include cytidine monophosphoacetylneuraminate-lactosylceramide alpha2,3-, sialyltransferase, CMP-acetylneuraminate-lactosylceramide-sialyltransferase, CMP-acetylneuraminic acid:lactosylceramide sialyltransferase, CMP-sialic acid:lactosylceramide-sialyltransferase, cytidine monophosphoacetylneuraminate-lactosylceramide, sialyltransferase, ganglioside GM3 synthetase, GM3 synthase, GM3 synthetase, and SAT 1. This enzyme participates in glycosphingolipid biosynthesis - ganglioseries and glycan structures - biosynthesis 2.

Structural studies

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 2EX0 and 2EX1.

References

• Basu S, Kaufman B, Roseman S (1973). "Enzymatic synthesis of glucocerebroside by a glucosyltransferase from embryonic chicken brain". J. Biol. Chem. 248 (4): 1388–94. doi:10.1016/S0021-9258(19)44311-1. PMID 4631392.
• Fishman PH, Bradley RM, Henneberry RC (1976). "Butyrate-induced glycolipid biosynthesis in HeLa cells: properties of the induced sialyltransferase". Arch. Biochem. Biophys. 172 (2): 618–26. doi:10.1016/0003-9861(76)90116-8. PMID 4022.
• Higashi H, Basu M, Basu S (1985). "Biosynthesis in vitro of disialosylneolactotetraosylceramide by a solubilized sialyltransferase from embryonic chicken brain". J. Biol. Chem. 260 (2): 824–8. doi:10.1016/S0021-9258(20)71172-5. PMID 3838172.

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