|3β-hydroxysteroid dehydrogenase/Δ-5-4 isomerase|
|EC number||CAS number||IntEnz||BRENDA||ExPASy||KEGG||MetaCyc||metabolic pathway|
3β- and steroid Δ-isomerase 1
|Alt. symbols||HSDB3, HSD3B|
3β- and steroid Δ-isomerase 2
3-β-HSD (or 3-β-hydroxysteroid dehydrogenase/Δ-5-4 isomerase) (HSD3B2 genes.
It is also known as delta 5-delta 4-isomerase, which catalyzes the oxidative conversion of delta 5-3 beta- hydroxysteroids to the delta 4-3-keto configuration and is, therefore, essential for the biosynthesis of all classes of hormonal steroids, namely progesterone, glucocorticoids, mineralocorticoids, androgens, and estrogens. The 3-beta HSD complex is responsible for the conversion of:
- pregnenolone to progesterone
- 17-alpha-pregnenolone to 17-alpha-progesterone
- dehydroepiandrosterone (DHEA) to androstenedione
- androstenediol to testosterone
3-β-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.
- a 3β-hydroxy-Δ5-steroid + NAD+ a 3-oxo-Δ5-steroid + NADH + H+
Humans express two 3-β-HSD isozymes, HSD3B1 (type I) and HSD3B2 (type II). The type I isoenzyme is expressed in placenta and peripheral tissues, whereas the type II 3β-HSD isoenzyme is expressed in the adrenal gland, ovary, and testis.
The systematic name of this enzyme class is 3β-hydroxy-Δ5-steroid:NAD+ 3-oxidoreductase. Other names in common use include:
- progesterone reductase
- Δ5-3β-hydroxysteroid dehydrogenase
- 3β-hydroxy-5-ene steroid dehydrogenase
- 3β-hydroxy steroid dehydrogenase/isomerase
- 3β-hydroxy-Δ5-C27-steroid dehydrogenase/isomerase
- 3β-hydroxy-Δ5-C27-steroid oxidoreductase
- 3β-hydroxy-5-ene-steroid oxidoreductase
- steroid-Δ5-3β-ol dehydrogenase
- 5-ene-3β-hydroxysteroid dehydrogenase
- 3β-hydroxy-5-ene-steroid dehydrogenase
A deficiency in the type II form through mutations in HSD3B2 is responsible for a rare form of congenital adrenal hyperplasia. No human condition has yet been linked to a deficiency in the type I enzyme. Its importance in placental progesterone production expression suggests that such a mutation would be embryonically lethal.
- 3α-Hydroxysteroid dehydrogenase (3α-HSD)
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