This archaeal enzyme, characterized from the methanogen?Methanocaldococcus jannaschii, catalyses a step in the synthesis of purine nucleotides. It differs from the orthologous bacterial/eukaryotic enzymes, which utilize 10-formyltetrahydrofolate rather than formate and ATP.?cf. EC?2.1.2.3, phosphoribosylaminoimidazolecarboxamide formyltransferase.