Fig. 1.

NAD⁺ biosynthetic pathways and redox metabolism of mammals. The de novo pathway for NAD⁺ biosynthesis is indicated in green, the salvage pathway is indicated in orange and the redox metabolism of NAD/NADP is indicated in blue. IDO indoleamine 2,3-dioxygenase, NAD ⁺ nicotinamide adenine dinucleotide, NaAD nicotinic acid dinucleotide, NADP nicotinamide adenine dinucleotide phosphate, NADK NAD⁺ kinase, NAM nicotinamide; NaMN nicotinic acid mononucleotide, NAMPT nicotinamide phosphoribosyltransferase, NAPT nicotinic acid phosphoribosyltransferase, NMNAT nicotinamide mononucleotide adenylyltransferase, NMN nicotinamide mononucleotide, NR nicotinamide riboside, NRK nicotinamide riboside kinase, TDO tryptophan 2,3-dioxygenase, Trp tryptophan