In enzymology, a nicotinate-nucleotide diphosphorylase (carboxylating) (EC 126.96.36.199) is an enzyme that catalyzes the chemical reaction
nicotinate D-ribonucleotide + diphosphate + CO2
pyridine-2,3-dicarboxylate + 5-phospho-alpha-D-ribose 1-diphosphate
The 3 substrates of this enzyme are nicotinate D-ribonucleotide, diphosphate, and CO2, whereas its two products are pyridine-2,3-dicarboxylate and 5-phospho-alpha-D-ribose 1-diphosphate.
This enzyme belongs to the family of glycosyltransferases, specifically the pentosyltransferases. The systematic name of this enzyme class is nicotinate-nucleotide:diphosphate phospho-alpha-D-ribosyltransferase (carboxylating). Other names in common use include quinolinate phosphoribosyltransferase (decarboxylating), quinolinic acid phosphoribosyltransferase, QAPRTase, NAD+ pyrophosphorylase, nicotinate mononucleotide pyrophosphorylase (carboxylating), and quinolinic phosphoribosyltransferase. This enzyme participates in nicotinate and nicotinamide metabolism.
As of late 2007, 9 structures have been solved for this class of enzymes, with PDB accession codes 1QAP, 1QPN, 1QPO, 1QPQ, 1QPR, 1X1O, 2B7N, 2B7P, and 2B7Q.