Reaction catalyzed by beta-galactoside alpha-2,3-sialyltransferase (2.4.3.4)

		+			=			+
	CMP-N-acetylneuraminate	+		beta-D-galactosyl-(1->3)-N-acetyl-alpha-D-galactosaminyl-R	=		CMP	+		alpha-N-acetylneuraminyl-(2->3)-beta-D-galactosyl-(1->3)-N-acetyl-alpha-D-galactosaminyl-R