Quinolinate phosphoribosyl transferase (QPRTase) or nicotinate-nucleotide pyrophosphorylase <db_xref db="EC" dbkey="2.4.2.19"/> is involved in the <i>de novo</i> synthesis of NAD in both prokaryotes and eukaryotes. It catalyses the reaction of quinolinic acid with 5-phosphoribosyl-1-pyrophosphate (PRPP) in the presence of Mg<sup>2+</sup> to give rise to nicotinic acid mononucleotide (NaMN), pyrophosphate and carbon dioxide [<cite idref="PUB00005289"/>, <cite idref="PUB00000163"/>]. Unlike <db_xref db="INTERPRO" dbkey="IPR004393"/>, this domain also includes the molybdenum transport system protein ModD.