InterPro domain: IPR027277

Proteins in this family includes nicotinate-nucleotide pyrophosphorylase ( 2.4.2.19 ) and putative pyrophosphorylase ModD.

Nicotinate-nucleotide pyrophosphorylase 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 ]. Human quinolinate phosphoribosyltransferase (also known as hQPRTase) is involved in the catabolism of quinolinic acid (QA) [ 3 ]. Elevation of QA levels in the brain has been linked to the pathogenesis of a range of neurodegenerative disorders [ 4 ].

ModD is found with molybdenum transport genes modABC in Rhodobacter capsulatus. However, disruption of modD causes only a 4-fold (rather than 500-fold for modA, modB, modC) change in the external molybdenum concentration required to suppress an alternative nitrogenase [ 5 ]. ModD proteins are highly similar to nicotinate-nucleotide pyrophosphorylase (also called quinolinate phosphoribosyltransferase). Their function is unknown.

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. Structural and kinetic characterization of quinolinate phosphoribosyltransferase (hQPRTase) from homo sapiens. J. Mol. Biol. 373, 755-63
4. Quinolinic acid phosphoribosyltransferase in human and rat brain: activity in Huntington's disease and in quinolinate-lesioned rat striatum. Brain Res. 336, 207-14
5. Characterization of Rhodobacter capsulatus genes encoding a molybdenum transport system and putative molybdenum-pterin-binding proteins. J. Bacteriol. 175, 3031-42