reductasa

Reductase, or reductasa in some languages, is a general term for enzymes that catalyze reduction reactions, transferring electrons to substrates and often using NADH or NADPH as electron donors. Reductases are a major subgroup of oxidoreductases (EC class 1) and participate in a wide range of physiological processes, from metabolism and detoxification to biosynthesis and drug activation.

Typical mechanisms involve the transfer of electrons from a reduced cofactor to the substrate, followed by chemical changes that add hydrogen or remove oxygen or other groups. Cofactor dependencies vary; many reductases use NADPH, some use NADH, and others rely on flavin cofactors (FAD or FMN), heme centers, or metal ions to facilitate electron transfer.

Major enzyme families include the short-chain dehydrogenase/reductase (SDR) and the aldo-keto reductase (AKR) superfamilies, which reduce carbonyl groups to alcohols in diverse substrates. Other notable examples are dihydrofolate reductase, which converts dihydrofolate to tetrahydrofolate and is a well-known target in cancer therapy, and 5-alpha-reductase, which reduces testosterone to dihydrotestosterone in steroid metabolism. Bacterial nitroreductases catalyze the reduction of nitro groups, contributing to antibiotic activation and resistance in some strains.

Biological roles are broad: reductases participate in steroid and fatty acid metabolism, xenobiotic detoxification, prostaglandin and vitamin metabolism, and the synthesis and modification of nucleotides and amino acids. Clinically and industrially, reductases influence drug efficacy, resistance, and biocatalysis, and they are frequently investigated as drug targets or tools for synthesis and biotransformation.