GlcA-beta-(1->2)-D-Man-alpha-(1->3)-D-Glc-beta-(1->4)-D-Glc-alpha-1-diphospho-ditransoctacis-undecaprenol 4-beta-mannosyltransferase (EC 2.4.1.251 GumI) is an enzyme with system name GDP-mannose:GlcA-beta-(1->2)-D-Man-alpha-(1->3)-D-Glc-beta-(1->4)-D-Glc-alpha-1-diphospho-ditransoctacis-undecaprenol 4-beta-mannosyltransferase.