Reaction catalyzed by lactosylceramide alpha-2,3-sialyltransferase (2.4.3.9)

		+			=			+
	CMP-N-acetylneuraminate	+		beta-D-galactosyl-1,4-beta-D-glucosylceramide	=		CMP	+		N-acetylneuraminyl-2,3-beta-D-galactosyl-1,4-beta-D-glucosylceramide