Nicotinamide Adenine Dinucleotide

Nicotinamide adenine dinucleotide, abbreviated NAD+, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.

In metabolism, NAD+ is involved in redox reactions, carrying electrons from one reaction to another. The coenzyme is, therefore, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD+. However, it is also used in other cellular processes, the most notable one being a substrate of enzymes that add or remove chemical groups from proteins, in posttranslational modifications. Because of the importance of these functions, the enzymes involved in NAD+ metabolism are targets for drug discovery.

In organisms, NAD+ can be synthesized from simple building-blocks (de novo) from the amino acids tryptophan or aspartic acid. In an alternative fashion, more complex components of the coenzymes are taken up from food as the vitamin called niacin. Similar compounds are released by reactions that break down the structure of NAD+. These preformed components then pass through a salvage pathway that recycles them back into the active form. Some NAD+ is also converted into nicotinamide adenine dinucleotide phosphate (NADP+); the chemistry of this related coenzyme is similar to that of NAD+, but it has different roles in metabolism.

Read more about Nicotinamide Adenine DinucleotidePhysical and Chemical Properties, Concentration and State in Cells, Biosynthesis, Functions, Pharmacology and Medical Uses, History

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Nicotinamide Adenine Dinucleotide - History
... the function of the nucleotide coenzyme in hydride transfer and identified the nicotinamide portion as the site of redox reactions ... A source of nicotinamide was identified in 1938, when Conrad Elvehjem purified niacin from liver and showed this vitamin contained nicotinic acid and ...
Aquacobalamin Reductase (NADPH)
... the two substrates of this enzyme are cob(II)alamin and nicotinamide adenine dinucleotide phosphate ion, whereas its 3 products are aquacob(III)alamin, nicotinamide adenine ... Other names in common use include aquacobalamin (reduced nicotinamide adenine dinucleotide phosphate), reductase, NADPH-linked aquacobalamin reductase, and NADPH2aquacob(III)alamin oxidoreductase ...
CDP-4-dehydro-6-deoxyglucose Reductase
... NAD(P)H + H+ The 4 substrates of this enzyme are CDP-4-dehydro-3,6-dideoxy-D-glucose, nicotinamide adenine dinucleotide ion, nicotinamide adenine dinucleotide phosphate ion, and water, whereas its 4 ...