NAMPT

Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme which catalyzes the conversion of nicotinamide (NAM) and phosphoribosyl-pyrophosphates to nicotinamide mononucleotide (NMN) in the mammalian nicotinamide adenine dinucleotide (NAD⁺) synthetic salvage pathway. NAMPT exists in two forms, intracellular NAMPT (iNAMPT) and extracellular NAMPT (eNAMPT).

iNAMPT levels are high in brown adipose tissue (BAT), liver and kidney, intermediate in white adipose tissue (WAT), lung, spleen, testes and skeletal muscle, and undetectable in brain and pancreas. eNAMPT, thought to be produced through post-translational modification of iNAMPT, is released into plasma predominantly from adipose tissue, where it catalyses the synthesis of NMN. Although intracellular NAMPT is a key enzyme in controlling NAD metabolism, eNAMPT has been reported to function as a cytokine, with many roles in physiology and pathology. Circulating eNAMPT has been associated with several metabolic and inflammatory disorders, including cancer.