GDP-Man:Man3GlcNAc2-PP-Dol alpha-1,2-mannosyltransferase activity
GDP-D-mannose:D-Man-alpha-(1->3)--D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-GlcNAc-diphosphodolichol alpha-1,2-mannosyltransferase activity