In enzymology, a monosialoganglioside sialyltransferase (EC 2.4.99.2) is an enzyme that catalyzes the chemical reaction

CMP-N-acetylneuraminate + D-galactosyl-N-acetyl-D-galactosaminyl-(N-acetylneuraminyl)-D-galactosyl-D-glucosylceramide ${\displaystyle \rightleftharpoons }$ CMP + N-acetylneuraminyl-D-galactosyl-N-acetyl-D-galactosaminyl-(N-acetylneuraminyl)-D-galactosyl-D-glucosylceramide

The 2 substrates of this enzyme are CMP-N-acetylneuraminate and D-galactosyl-N-acetyl-D-galactosaminyl-(N-acetylneuraminyl)-D-galactosyl-D-glucosylceramide, whereas its 2 products are CMP and N-acetylneuraminyl-D-galactosyl-N-acetyl-D-galactosaminyl-(N-acetylneuraminyl)-D-galactosyl-D-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:D-galactosyl-N-acetyl-D-galactosaminyl-(N-ac etylneuraminyl)-D-galactosyl-D-glucosylceramide N-acetylneuraminyltransferase.

• Rearick JI, Sadler JE, Paulson JC, Hill RL (1979). "Enzymatic characterization of beta D-galactoside alpha2 leads to 3 sialyltransferase from porcine submaxillary gland". J. Biol. Chem. 254 (11): 4444–51. PMID 438198.
• Yip MC (1973). "The enzymic synthesis of disialoganglioside: rat brain cytidine-5'-monophospho-N-acetylneuraminic acid: monosialoganglioside (G M1) sialyltransferase". Biochim. Biophys. Acta. 306 (2): 298–306. doi:10.1016/0005-2760(73)90235-X. PMID 4351506.