Figure 3.

NAD+ Biosynthesis. De Novo NAD+ synthesis starts with the conversion of Nicotinic Acid to Nicotinic Acid Mononucleotide (NAMN) by nicotinic acid phosphoribosyltransferase (npt). NAMN is then converted to Nicotinic acid adenine dinucleotide (NAAD) by nicotinic acid/nicotinamide mononucleotide adenylyltransferase (Nmnat). NAAD is finally converted to NAD+ by NAD synthetase. The salvage pathway utilizes Nicotinamide, which is converted to Nicotinamide mononucleotide (NMN) by nicotinamide phosphoribosyltranferase (Nampt). Nmnat then converts NMN to NAD+. The salvage pathway is continually active as NAD+ is degraded by PARP-1 and other proteins (adapted from Yang and Sauve, 2006).