<p>Phosphoribosylaminoimidazole-succinocarboxamide synthase (<db_xref db="EC" dbkey="6.3.2.6"/>) (SAICAR synthetase) catalyzes the seventh step in the <i>de novo</i> purine biosynthetic pathway; the ATP-dependent conversion of 5'-phosphoribosyl-5-aminoimidazole-4-carboxylic acid and aspartic acid to SAICAR [<cite idref="PUB00004940"/>].</p><p>In bacteria (purC), fungi (ADE1) and plants (Pur7), SAICAR synthetase is a monofunctional protein; in animals it is the N-terminal domain of a bifunctional enzyme that also catalyse phosphoribosylaminoimidazole carboxylase (AIRC) activity (see <db_xref db="INTERPRO" dbkey="IPR000031"/>).</p>