Reaction catalyzed by geranylgeranylglycerol-phosphate geranylgeranyltransferase (2.5.1.42)

		+			=			+
	geranylgeranyl diphosphate	+		3-(O-geranylgeranyl)-sn-glycerol 1-phosphate	=		diphosphate	+		2,3-bis-(O-geranylgeranyl)-sn-glycerol 1-phosphate