The Pre-B-cell colony-Enhancing Factor (PBEF) or Nampt is 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. This protein is thought to be involved in many important biological processes (metabolism，stress response and aging).
