Nicotinamide phosphoribosyltransferase (NAmPRTase or Nampt) also known as pre-B-cell colony-enhancing factor 1 (PBEF1) or visfatin is an enzyme that in humans is encoded by the PBEF1 gene. This protein is the rate-limiting enzyme in the nNicotinamide adenine dinucleotide (NAD+) salvage pathway that converts nicotinamide to nicotinamide mononucleotide in mammals to enable NAD+ biosynthesis. NAMPT has also been reported to be a cytokine (PBEF) that promotes B cell maturation and inhibits neutrophil apoptosis.