The HisF subunit of Thermotoga maritima imidazole glycerol phosphate (ImGP) synthase catalyses the reaction of N'-((5'-phosphoribulosyl)formimino)-5-aminoimidazole-4-carboxamide-ribonucleotide (PRFAR) with ammonia to form an imine, loss of 5-aminoimidazole-4-carboxamide ribotide (AICAR), and the subsequent cyclisation to form ImGP. This reaction is the second half of the fifth step in histidine biosynthesis. ImGP and AICAR are used in histidine and purine biosynthesis respectively. Ammonia is delivered to the active site directly from an associated subunit, HisH, which hydrolyses glutamine to glutamate.
Defined by 2 residues: ASP:A-23 [auth A-11]ASP:A-142 [auth A-130]