Reaction catalyzed by GDP-Man:Man1GlcNAc2-PP-dolichol alpha-1,3-mannosyltransferase (2.4.1.132)

		+			=			+
	GDP-alpha-D-mannose	+		beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc-diphosphodolichol	=		GDP	+		alpha-D-Man-(1->3)-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc-diphosphodolichol