Wikipedia:Today's featured article/November 26, 2009

Nicotinamide adenine dinucleotide (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, with one nucleotide containing an adenine base and the other containing 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. However, it is also used in other cellular processes, notably as a substrate of enzymes that add or remove chemical groups from proteins, in posttranslational modifications. Due to the importance of these functions, the enzymes involved in NAD⁺ metabolism are targets for drug discovery. In organisms, NAD⁺ can be synthesized from basic building blocks (de novo) from the amino acids tryptophan or aspartic acid. 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. (more...)

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