Figure 1.

Metabolism of NAD in Plants.

The steps involved in the de novo pathway are indicated by blue arrows, the four-step salvage pathway (start from NIM) is indicated by a black arrow, and two-step salvage pathway is indicated by green arrows. AO, aspartate oxidase; NaAD, nicotinate adenine dinucleotide; NAD, nicotinamide adenine dinucleotide; NaMN, nicotinate mononucleotide; NaMNAT, NaMN adenylyltransferase; NaPRT, nicotinate phosphoribosyltransferase; NIC, nicotinamidase; PARP, poly(ADP-ribose) polymerase; QPT, quinolinate phosphoribosyltransferase; QS, quinolinate synthase; SIRT, sirtuins (NAD dependent protein deacetylases).