β-galactoside α-2,3-sialyltransferase

The acceptor is Galβ1,3GalNAc-R, where R is H, a threonine or serine residue in a glycoprotein, or a glycolipid. Lactose can also act as acceptor. May be identical with EC 2.4.99.2 monosialoganglioside sialyltransferase. Reaction: CMP-N-acetylneuraminate + β-D-galactosyl-(1→3)-N-acetyl-α-D-galactosaminyl-R = CMP + α-N-acetylneuraminyl-(2→3)-β-D-galactosyl-(1→3)-N-acetyl-α-D-galactosaminyl-R