InterPro domain: IPR004393

Nicotinate-nucleotide pyrophosphorylase ( 2.4.2.19 ), also known as quinolinate phosphoribosyltransferase (decarboxylating), catalyses the conversion of nicotinate D-ribonucleotide, pyrophosphate and carbon dioxide into pyridine-2,3-dicarboxylate and 5-phospho-alpha-D-ribose 1-diphosphate. This enzyme is a type II phosphoribosyltransferase which provides the de novo source of nicotinate mononucleotide (NAMN) for NAD biosynthesis in both prokaryotes and eukaryotes [ 1 , 2 ].

Structural studies have shown that the active form of this enzyme is a homodimer with an unsual fold [ 3 , 4 , 5 ]. The N-terminal forms a mixed alpha/beta domain, while the C-terminal region forms a multi-stranded, open alpha/beta barrel. The active site is found at the C-terminal ends of the beta strands of the alpha/beta barrel, and is bordered by the N-terminal domain of the second subunit of the dimer. It contains several conserved charged residues thought to be important determinants of substrate binding and catalysis.

1. Nicotinamide adenine dinucleotide biosynthesis and pyridine nucleotide cycle metabolism in microbial systems. Microbiol. Rev. 44, 83-105
2. Quinolinate phosphoribosyltransferase: kinetic mechanism for a type II PRTase. Biochemistry 41, 3520-8
3. A new function for a common fold: the crystal structure of quinolinic acid phosphoribosyltransferase. Structure 5, 47-58
4. Crystal structure of quinolinic acid phosphoribosyltransferase from Mmycobacterium tuberculosis: a potential TB drug target. Structure 6, 1587-99
5. Crystal structure of a type II quinolic acid phosphoribosyltransferase (TM1645) from Thermotoga maritima at 2.50 A resolution. Proteins 55, 768-71