<p>The last two steps of <i>de novo</i> purine biosynthesis are: <ul><li>i) conversion of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranosyl 5'-monophosphate (AICAR) to 5-formaminoimidazole-4-carboxamide-1-beta-D-ribofuranosyl 5'-monophosphate (FAICAR)</li><li>ii) conversion of FAICAR to inosine5'-monophopsphate (IMP)</li></ul>In bacteria and eukaryotes, these steps are catalysed by the well-characterised bifunctional enzyme PurH [<cite idref="PUB00025174"/>]. Archaea do not appear to posses PurH, however, and perform these reactions by a different mechanism [<cite idref="PUB00034499"/>]. In archaea, step i) is catalysed by the well-conserved PurP protein, while step ii) is catalysed by the PurO enzyme in some (though not all) species [<cite idref="PUB00034500"/>, <cite idref="PUB00013793"/>].</p> <p>This entry represents the C-terminal domain of PurP, which is homologous to the ATP-GRASP fold and thus may be involved in ATP-binding. It is almost always found in association with <db_xref db="INTERPRO" dbkey="IPR010672"/>.</p> IMP biosynthesis enzyme PurP, C-terminal