Fig. 1.

Schematic representation of nicotinamide phosphoribosyltransferase (NAMPT) biological function. The enzyme is involved in synthesis of nicotinamide adenine dinucleotide (NAD), which is an important metabolite involved in regulation of cellular processes. In mammals, the synthesis of NAD occurs in two steps: first, formation of nicotinamide mononucleotide (NMN) from nicotinamide (NAM) takes place, and then NAD is formed from NMN in the second step. The X-ray structure of NMN-bound NAMPT is shown (PDB ID: 2H3B) representing a functional dimeric form. For completion of NAD cycling, the deacetylation of NAD+ to NAM takes place in presence of Sirtuins (SIRT1,2). The X-ray structure of SIRT2 is depicted (PDB ID: −4Y6L). The NAMPT protein is a potential drug target and the drug-bound NAMPT crystal structure is shown at the top (PDB ID: 4O13)[23].