IGPS catalyzes the conversion of PRFAR and glutamine to IGP, AICAR and glutamate. The HisF subunit catalyzes the cyclization activity that produces IGP and AICAR from PRFAR using the ammonia provided by the HisH subunit (By similarity). hisF IGP synthase subunit HisF Imidazole glycerol phosphate synthase subunit HisF BL0685 IGP synthase cyclase subunit MSLAVRVIPCLDVDAGRVVKGVHFENLKDAGDPVELAAEYYRQRADEITFLDVTASSSHRNTMIDVVSRTAEQVFIPMTVGGGVRTPEDVDSLLRCGADKVGVNTAAINDPSLISRVADRFGNQVLVLSVDARREKGEQHTQSGFEVTTMGGRKSTGIDAIWWVKRAEQLGAGEILLNSMDADGTKEGFDLEMIRAVRKEVKIPIIASGGAGKVEDFPPAIEAGADAVLAASVFHYGILTIADVKAELKKHGYTVR ImGP synthase subunit HisF HIS6_BIFLO 256