- Source: N-acetyllactosaminide alpha-2,3-sialyltransferase
In enzymology, a N-acetyllactosaminide alpha-2,3-sialyltransferase (EC 2.4.99.6) is an enzyme that catalyzes the chemical reaction
CMP-N-acetylneuraminate + beta-D-galactosyl-1,4-N-acetyl-D-glucosaminyl-glycoprotein
⇌
{\displaystyle \rightleftharpoons }
CMP + alpha-N-acetylneuraminyl-2,3-beta-D-galactosyl-1,4-N-acetyl-D- glucosaminyl-glycoprotein
Thus, the two substrates of this enzyme are CMP-N-acetylneuraminate and beta-D-galactosyl-1,4-N-acetyl-D-glucosaminyl-glycoprotein, whereas its 3 products are CMP, alpha-N-acetylneuraminyl-2,3-beta-D-galactosyl-1,4-N-acetyl-D-, and glucosaminyl-glycoprotein.
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:beta-D-galactosyl-1,4-N-acetyl-D-glucosaminy l-glycoprotein alpha-2,3-N-acetylneuraminyltransferase. Other names in common use include sialyltransferase, cytidine, monophosphoacetylneuraminate-beta-galactosyl(1-, >4)acetylglucosaminide alpha2->3-sialyltransferase, alpha2->3 sialyltransferase, and SiaT. This enzyme participates in 4 metabolic pathways: keratan sulfate biosynthesis, glycosphingolipid biosynthesis - lactoseries, glycan structures - biosynthesis 1, 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
Van den Eijnden DH, Schiphorst WE (1981). "Detection of beta-galactosyl(1 leads to 4)N-acetylglucosaminide alpha(2 leads to 3)-sialyltransferase activity in fetal calf liver and other tissues". J. Biol. Chem. 256 (7): 3159–62. doi:10.1016/S0021-9258(19)69581-5. PMID 7204397.