Nicotinamide adenine dinucleotide phosphate

Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or TPN in older notation (triphosphopyridine nucleotide), is a coenzyme used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent.

NADPH is the reduced form of NADP. NADP differs from NAD in the presence of an additional phosphate group on the 2' position of the ribose ring that carries the adenine moiety.

In plants
In chloroplasts, NADP is reduced by ferredoxin-NADP reductase in the last step of the electron chain of the light reactions of photosynthesis. The NADPH produced is then used as reducing power for the biosynthetic reactions in the Calvin cycle of photosynthesis. In its energized state, it is NADPH, now holding an extra electron. It is used primarily to create the proton gradient in chloroplasts during the light-dependent reactions.

In animals
The oxidative phase of the pentose phosphate pathway is the major source of NADPH in cells, producing approximately 60% of the NADPH required.

NADPH provides the reducing equivalents for biosynthetic reactions and the oxidation-reduction involved in protecting against the toxicity of ROS (reactive oxygen species), allowing the regeneration of GSH (reduced glutathione). NADPH is also used for anabolic pathways, such as lipid synthesis, cholesterol synthesis, and fatty acid chain elongation.

The NADPH system is also responsible for generating free radicals in immune cells. These radicals are used to destroy pathogens in a process termed the respiratory burst.

It is the source of reducing equivalents for cytochrome P450 hydroxylation of aromatic compounds, steroids, alcohols, and drugs.