Skip to main content
. Author manuscript; available in PMC: 2011 Jul 1.
Published in final edited form as: Pharmacol Res. 2010 Jan 18;62(1):42–47. doi: 10.1016/j.phrs.2010.01.006

Figure 2.

Figure 2

NAD biosynthetic pathways from nicotinamide and nicotinic acid in mammals. The de novo pathway from tryptophan is not shown in this scheme. These pathways, are conserved throughout vertebrates. Nicotinamide is the main precursor for NAD biosynthesis in mammals. NPT, NAMPT, and NMNAT are nicotinic acid phosphoribosyltransferase, nicotinamide phosphoribosyltransferase, and nicotinamide/nicotinic acid mononucleotide adenylyltransferase, respectively. Multiple enzymes break NAD down to nicotinamide and ADP-ribose, but only sirtuins are shown in this scheme. Nic, nicotinamide; NA, nicotinic acid; NaMN, nicotinic acid mononucleotide; NMN, nicotinamide mononucleotide.