Reaction catalyzed by beta-D-galactosyl-(1->3)-N-acetyl-beta-D-galactosaminide alpha-2,3-sialyltransferase (2.4.3.2)

		+			=			+
	CMP-N-acetyl-beta-neuraminate	+		[asialofetuin]-(O-3-(beta-D-Gal-(1->3)-beta-D-GalNAc-(1->)))-L-serine	=		CMP	+		[protein]-(O-3-(alpha-Neu5Ac-(2->3)-beta-D-Gal-(1->3)-beta-D-GalNAc-(1->)))-L-serine