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5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer. There are three isoenzymes of 5-alpha reductase, which vary in different tissues with age. 5α-reductases catalyze the following chemical reaction: :a 3-oxo-5α-steroid + acceptor a 3-oxo-Δ4-steroid + reduced acceptor Thus, the two substrates of these enzymes are a 3-oxo-5α-steroid and acceptor, whereas its two products are 3-oxo-Δ4-steroid and a reduced acceptor. == Production and activity == The enzyme is produced in many tissues in both males and females, in the reproductive tract, testes and ovaries, skin, seminal vesicles, prostate, epididymis and many organs, including the Nervous System. There are three isoenzymes of 5-alpha reductase: steroid 5α-reductase 1, 2, and 3 (SRD5A1, SRD5A2 and SRD5A3).〔 5α-reductases act on 3-oxo (3-keto), Δ4,5 C 19/C21 steroids as its substrates. “3-keto” refers to the double bond of the third carbon to oxygen. Carbons 4 and 5 also have a double bond, represented by 'Δ 4, 5'. The reaction involves a stereospecific and permanent break of the Δ 4, 5 with the help of NADPH as a cofactor. A hydride anion (H−) is also placed on the α face at the fifth carbon, and a proton on the β face at carbon 4. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「5-alpha reductase」の詳細全文を読む スポンサード リンク
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