NADH IUPAC/IUBMB proposes the abbreviations NAD+ for the oxidised form, NADH for the reduced form and NAD in general. Sometimes NAD takes place NAD+ and NADH2 takes place NADH. Compared to nicotinamide adenine adenine dinucleotide phosphate and nicotinic acid adenine dinucleotide phosphate, two otherwise almost identically constructed coenzymes, both of which have a further phosphate residue on the 2’C atom of the adenosine, there is only one normal hydroxyl group in the NAD.
The reducing agent used is mainly NADPH, which has a correspondingly low NADP+/NADPH ratio. The result is NAD+ and hydrogen.
NAD+ is produced in the body from nicotinic acid and nicotinamide as well as from the degradation products of the amino acid tryptophan. Node of both reaction pathways is nicotinate D-ribonucleotide, which can be formed directly from nicotinic acid by means of nicotinate phosphoribosyltransferase, or which is formed from the tryptophan degradation product quinolinic acid by means of the enzyme quinolinate phosphoribosyltransferase.
This absorbs light at a wavelength of 260 nm, which explains the common absorption maximum in the 260 nm range shown in the diagram. The reason for this is that the absorption of the oxidized, mesomeric nicotinamide ring, which also absorbs at 260 nm, is superimposed with the absorption of adenine and thus ensures increased absorption at 260 nm. The molar extinction coefficient ԑ of NADH at 339 nm is ԑ = 6200 l/. The amount of the converted substrate can be photometrically traced by changing the absorption at 340 nm, the concentration can then be determined by means of the Lambert-Beer law.