Reaction catalyzed by digalactosyldiacylglycerol synthase (2.4.1.241)

		+			=			+
	UDP-alpha-D-galactose	+		1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol	=		UDP	+		1,2-diacyl-3-O-[alpha-D-galactosyl-(1->6)-beta-D-galactosyl]-sn-glycerol