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3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD) () is an enzyme that catalyzes the biosynthesis of progesterone from pregnenolone, 17α-hydroxyprogesterone from 17α-hydroxypregnenolone, and androstenedione from dehydroepiandrosterone (DHEA) in the adrenal gland. It is the only enzyme in the adrenal pathway of corticosteroid synthesis that is not a member of the cytochrome P450 family.〔 In humans, there are two 3β-HSD isozymes encoded by the HSD3B1 and HSD3B2 genes. 3β-HSD is also known as delta Δ5-4-isomerase, which catalyzes the oxidative conversion of Δ5-3-β-hydroxysteroids to the Δ4-3-keto configuration and is, therefore, essential for the biosynthesis of all classes of hormonal steroids, namely progesterone, glucocorticoids, mineralocorticoids, androgens, and estrogens.〔 The 3β-HSD complex is responsible for the conversion of: * Pregnenolone to progesterone * 17α-Hydroxypregnenolone to 17α-hydroxyprogesterone * DHEA to androstenedione * Androstenediol to testosterone * Androstadienol to androstadienone ==Reaction== 3β-HSD belongs to the family of oxidoreductases, to be specific, those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. This enzyme participates in C21-steroid hormone metabolism and androgen and estrogen metabolism. 3β-HSD catalysis|catalyzes the chemical reaction: :a 3β-hydroxy-Δ5-steroid + NAD+ a 3-oxo-Δ5-steroid + NADH + H+ Thus, the two substrates of this enzyme are 3β-hydroxy-Δ5-steroid and NAD+, whereas its three products are 3-oxo-Δ5-steroid, NADH, and H+. 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「3beta-Hydroxysteroid dehydrogenase」の詳細全文を読む スポンサード リンク
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