NADPHdependent

NADPH-dependent refers to enzymes or metabolic reactions that require nicotinamide adenine dinucleotide phosphate in its reduced form (NADPH) to donate reducing power. In these reactions, NADPH provides a hydride to substrates, enabling reductive transformations that are essential for biosynthesis, detoxification, and redox balance. This is distinct from NADH, which is primarily used to generate ATP in catabolic pathways.

Cells generate and maintain NADPH through several routes, with the oxidative phase of the pentose phosphate pathway being a major source. Other contributors include cytosolic and mitochondrial enzymes such as malic enzyme and certain isocitrate dehydrogenases. NADPH is kept at relatively high cellular concentrations to support anabolic processes and antioxidant defenses.

Functions commonly powered by NADPH include fatty acid and cholesterol synthesis, nucleotide biosynthesis, and the maintenance of redox homeostasis. NADPH is also critical for detoxification reactions, where enzymes such as glutathione reductase and thioredoxin reductase regenerate antioxidant systems, and for the activity of many detoxification and drug-metabolizing systems that rely on NADPH to furnish electrons.

Examples of NADPH-dependent enzymes cover a broad range, including glutathione reductase, thioredoxin reductase, nitric oxide synthases, cytochrome P450 reductase, and ferredoxin-NADP+ reductase. In research and biotechnology, NADPH availability can influence the efficiency of engineered metabolic pathways, prompting strategies to boost NADPH supply to improve yields of NADPH-dependent products.