In enzymology, a lactosylceramide alpha-2,3-sialyltransferase (EC 2.4.99.9) is an enzyme that catalyzes the chemical reaction 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.
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 2EX0 and 2EX1.