3-beta-HSD

• OMIM: 201810

3β -hydroxysteroid dehydrogenase ( 3β -HSD ) are called enzymes that reduce steroids in the 3β -hydroxyl group to the ketone, while the rearrangement of the double bond of the 5 - to catalyze the 4-position. This reaction is required in vertebrates in the biosynthesis of progesterone from pregnenolone as well as in the conversion of DHEA to androstenedione or 17α -hydroxy- pregnenolone to 17α - hydroxyprogesterone.

3β -HSD are transmembrane proteins and localize to the endoplasmic reticulum and mitochondria. In humans three isoforms paralogs are known, that are expressed in different tissue types: 3β - HSD, mainly in the mammary gland, placenta and skin; 3β -HSD II especially in adrenal glands, testes and ovaries. Mutations in the HSD3B2 gene are responsible for a adrenogenital syndrome type 2 ( congenital adrenal hyperplasia ). The third human enzyme of this protein family is 3β -HSD type 7, an enzyme of the bile acid formation from cholesterol.

Catalyzed reactions

NAD ⇔ ⇔ NADH / H

Pregnenolone is converted to progesterone. It takes place successively dehydrogenation to ketone and a rearrangement of the double bond. A further reaction is the conversion of DHEA to androstenedione.

Structure reference

Structural model of HSD3B1: JPEG from