NADPH

NADPH, or reduced nicotinamide adenine dinucleotide phosphate, is a coenzyme that carries reducing power between biochemical reactions. It is the reduced form of NADP+ and can donate electrons to other molecules during oxidation-reduction reactions. NADPH is used extensively in cells to drive reactions that require chemical reduction .^1,2

One major role of NADPH is supporting biosynthesis. Its reducing power is used in pathways that construct molecules such as fatty acids and cholesterol. NADPH is also central to cellular antioxidant systems. It helps maintain molecules such as glutathione and thioredoxin in their reduced forms, supporting systems that limit oxidative damage and maintain cellular redox balance .^1,2

Cells regenerate NADPH from NADP+ through several metabolic reactions. In the cytosol, an important source is the oxidative phase of the pentose phosphate pathway, in which oxidation of glucose-6-phosphate and 6-phosphogluconate produces NADPH. The relative contribution of different NADPH-producing pathways varies among tissues and cellular compartments .^1,2

NADPH is closely related to NADH but serves a somewhat different metabolic role. NADH is used predominantly to transfer electrons from fuel oxidation toward energy production, whereas NADPH is used predominantly for reductive biosynthesis and redox defense. NADPH can also supply electrons to NADPH oxidases, which generate reactive oxygen species for functions such as cellular signaling and antimicrobial defense .^1,2