What NAD+ is, in plain English.
NAD+, nicotinamide adenine dinucleotide, is a coenzyme found in every living cell, not a peptide, and the largest fill in the range at 500mg. Chemically it is two nucleotides joined through their phosphate groups, one carrying adenine and the other nicotinamide, a form of vitamin B3; its molecular formula is C21H27N7O14P2, its molecular weight about 663.4 g/mol and its CAS number 53-84-9. It was discovered in 1906 by the British biochemists Arthur Harden and William John Young, and in 1936 Otto Warburg showed how it works: the nicotinamide end is where electrons are taken up and given back. That is its first role. It carries electrons in the redox reactions cells use to turn nutrients into ATP, cycling between NAD+ and its reduced form, NADH. Its second role is as a substrate that is used up: the sirtuins and the PARPs, two families of enzymes involved in DNA repair, gene regulation and the cell's stress responses, consume it, as does the enzyme CD38, so cells must keep remaking it, from the amino acid tryptophan or by recycling vitamin B3 compounds. It is commonly researched for its role in mitochondrial energy metabolism, in those sirtuin and PARP pathways, and in longevity and metabolic models. The idea that its levels fall with age is what drew ageing research to it, though the human evidence for that decline is inconsistent and may depend on the tissue measured. Supplied as 500mg of freeze-dried powder per vial, for reconstitution with bacteriostatic water; store at 2–8°C.
