Reaction catalyzed by phosphatidyl-myo-inositol dimannoside synthase (2.4.1.346)

		+			=			+
	GDP-alpha-D-mannose	+		2-O-alpha-D-mannosyl-1-phosphatidyl-1D-myo-inositol	=		GDP	+		2,6-di-O-alpha-D-mannosyl-1-phosphatidyl-1D-myo-inositol