<p>Phosphoribosylglycinamide synthetase (<db_xref db="EC" dbkey="6.3.4.13"/>) (GARS) (phosphoribosylamine glycine ligase) [<cite idref="PUB00002527"/>] catalyses the second step in the <i>de novo</i> biosynthesis of purine. The reaction catalysed by phosphoribosylglycinamide synthetase is the ATP-dependent addition of 5-phosphoribosylamine to glycine to form 5'phosphoribosylglycinamide:<reaction>ATP + 5-phosphoribosylamine + glycine = ADP + P<sub>i</sub> + 5'-phosphoribosylglycinamide</reaction>In bacteria, GARS is a monofunctional enzyme (encoded by the purD gene). Inyeast, GARS is part of a bifunctional enzyme (encoded by the ADE5/7 gene) in conjunction with phosphoribosylformylglycinamidine cyclo-ligase (AIRS) (<db_xref db="INTERPRO" dbkey="IPR000728"/>). In higher eukaryotes, GARSis part of a trifunctional enzyme in conjunction with AIRS (<db_xref db="INTERPRO" dbkey="IPR000728"/>) and with phosphoribosylglycinamide formyltransferase (GART) (<db_xref db="INTERPRO" dbkey="IPR001555 "/>), forming GARS-AIRS-GART.</p>