Reaction catalyzed by mannosylglucosyl-3-phosphoglycerate synthase (2.4.1.270)

		+			=			+
	UDP-mannose	+		2-O-(alpha-D-glucopyranosyl)-3-phospho-D-glycerate	=		UDP	+		2-(2-O-(alpha-D-mannopyranosyl)-alpha-D-glucopyranosyl)-3-phospho-D-glycerate