1. Figure 5 Pathways leading to the NAD+ production
Figure 5 | Pathways leading to the NAD+ production. De novo synthesis of NAD+ begins with tryptophan (purple) and includes five enzymes (not represented on the figure): tryptophan 2,3-dioxygenase (hepatic) or indoleamine 2,3-dioxygenase 1 (nonhepatic), arylformamidase, kynurenine 3-mono oxygenase, kynureninase and 3-hydroxyanthranilic acid dioxygenase. NA leads to NAD+ synthesis through the Preiss–Handler pathway (green), and shares the same intermediate, NaMN, as de novo synthesis. In yeast, NAM is converted into NA by the nicotinamidase Pnc1p (yellow), while in mammals NAM leads to the production of NMN, catalysed by the enzyme NAMPT (pink). NR is converted to NMN in both mammals and yeast; however, yeast can also convert NR to NAM via the enzymes Urh1p and Pnp1p (blue). Reactions not catalysed/present in mammals indicated by dashed lines. Abbreviations: NA, nicotinic acid; NAD+, nicotinamide adenine dinucleotide; NADS, NAD+ synthase; NAM, nicotinamide; NAMPT, nicontinamide phosphoribosyltransferase; NAPT, nicotinic acid phosphoribosyltransferase; NMN, NAM mononucleotide; NMNAT, nicotinamide mononucleotide adenylyl transferase; NR, nicotinamide riboside; NRK, nicotinamide riboside kinase; Pnc1p, pyrazinamidase/nicotinamidase 1; Pnp1p, purine nucleoside phosphorylase; QPRT, quinolinate phosphoribosyltransferase; Urh1p, uridine hydrolase.
Menzies, K. J. et al. (2015) Protein acetylation in metabolism—metabolites and cofactors
Nat. Rev. Endocrinol. doi: /nrendo