This gene encodes a protein that catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, one step in the biosynthesis of nicotinamide adenine dinucleotide. The protein belongs to the nicotinic acid phosphoribosyltransferase (NAPRTase) family and is thought to be involved in many important biological processes, including metabolism, stress response and aging. This gene has a pseudogene on chromosome 10. [provided by RefSeq, Feb 2011],catalytic activity:Nicotinamide D-ribonucleotide + diphosphate = nicotinamide + 5-phospho-alpha-D-ribose 1-diphosphate.,caution:Was originally (PubMed:8289818) thought to be a cytokine which acts on early B-lineage precursor cells, by enhancing the effect of IL-7 and SCF on pre-B-cell colony formation.,function:Catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, an intermediate in the biosynthesis of NAD. It is the rate limiting component in the mammalian NAD biosynthesis pathway.,pathway:Cofactor biosynthesis, NAD(+) biosynthesis, nicotinamide ribonucleotide from 5-phospho-alpha-D-ribose 1-diphosphate and nicotinamide: step 1/1.,similarity:Belongs to the NAPRTase family.,tissue specificity:Expressed in large amounts in bone marrow, liver tissue, and muscle. Also present in heart, placenta, lung, and kidney tissues.,
