Nicotinamide adenine dinucleotide phosphate
, in older notation triphosphopyridine nucleotide, TPN
) is 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+, and NADP+ is the oxidized form of NADPH.
, NADP is reduced by ferredoxin-NADP+ reductase
in last step of the electron chain of the light reactions
. The NADPH produced is then used as reducing power for the biosynthetic reactions in the Calvin cycle
NADP ions in photosynthesis may be seen as 'dragging' hydrogen ions along with them (in the light-dependent cycles), which are used by the light-independent (Calvin) cycles to produce carbohydrates.
The oxidative phase of the pentose phosphate pathway
is the major source of NADPH in cells.
NADPH provides the reducing equivalents for biosynthetic reactions and for oxidation-reduction involved in protection against the toxicity of ROS (reactive oxygen species).
NADPH is also used for anabolic pathways, such as lipid synthesis, cholesterol synthesis and fatty acid chain elongation.
It is the source of reducing equivalents for cytochrome 450 hydroxylation of aromatic compounds, steroids, alcohols, and drugs.