In the nicotinamide adenine dinucleotide (NAD(+)) salvage pathway, NAD(+) is synthesized from the vitamin B3 derivatives nicotinate (NA) and nicotinamide (NAM), and from β-nicotinamide D-riboside (NR) or nicotinate riboside (NAR). These compounds can be acquired either from the diet or as a by-product of NAD(+)-consuming enzymes. NAD(+) synthesis occurs predominantly in the cytosol. NAD(+) is then transported to other organelles including the nucleus and the mitochondrion. NAD(+) can also be phosphorylated to form NADP(+). NAD(+) and NADP(+) form NAD(+)/NADH and NADP(+)/NADPH redox couples that are essential for maintaining cellular redox homeostasis and metabolic processes. The NAD(+)/NADH redox couple is involved in catabolic processes such as glycolysis and mitochondrial oxidative phosphorylation, while the NADP(+)/NADPH redox couple is required for anabolic processes such as fatty acid biosynthesis and oxidative-stress defence. NAD(+) is also an essential co-substrate for NAD(+)-consuming enzymes, including NAD(+) glycohydrolases (e.g. Sarm), protein deacetylase sirtuins, and ADP-ribose polymerases (PARPs). (Adapted from PMID:33353981 and PMID:22404877.)