Nicotinamide adenine dinucleotide (NAD+)
Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. NADH is the reduced form of NAD, and NAD+ is the oxidized form of NAD. It forms NADP with the addition of a phosphate group to the 2' position of the adenosyl nucleotide through an ester linkage.
NAD is used extensively in glycolysis and the citric acid cycle of cellular respiration. The reducing potential stored in NADH can be converted to ATP through the electron transport chain or used for anabolic metabolism.
Nicotinamide adenine dinucleotide phosphate (NADP+)
NADP is used in anabolic reactions, such as fatty acid and nucleic acid synthesis, that require NADPH as a reducing agent. In chloroplasts, NADP is an oxidising agent important in the preliminary reactions of photosynthesis. The NADPH produced by photosynthesis is then used as reducing power for the biosynthetic reactions in the Calvin cycle of photosynthesis.
- MH2 + NAD+ → NADH + H+ + M: + energy, where M is a metabolite.
Two hydrogen ions (a hydride ion and an H+ ion) are transferred from the metabolite. One electron is transferred to the positively-charged nitrogen, and one hydrogen attaches to the carbon atom opposite to the nitrogen.
The change upon nicotinamide group when NAD+ is reduced
The human body synthesizes NAD from the vitamin niacin in the form of nicotinic acid or nicotinamide.
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