Quinolinate phosphoribosyl transferase (QPRTase) or nicotinate-nucleotide pyrophosphorylase EC:2.4.2.19 is involved in the de novo synthesis of NAD in both prokaryotes and eukaryotes. It catalyzes the reaction of quinolinic acid with 5-phosphoribosyl-1-pyrophosphate (PRPP) in the presence of Mg2+ to give rise to nicotinic acid mononucleotide (NaMN), pyrophosphate and carbon dioxide. The QA substrate is bound between the C-terminal domain of one subunit, and the N-terminal domain of the other. The N-terminal domain has an alpha/beta hammerhead fold.
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