Hsd3b1

Function

A bifunctional enzyme responsible for the oxidation and isomerization of 3beta-hydroxy-Delta(5)-steroid precursors to 3-oxo-Delta(4)-steroids, an essential step in steroid hormone biosynthesis. Specifically catalyzes the conversion of pregnenolone to progesterone, 17alpha-hydroxypregnenolone to 17alpha-hydroxyprogesterone, dehydroepiandrosterone (DHEA) to 4-androstenedione, and androstenediol to testosterone. Additionally, catalyzes the interconversion between 3beta-hydroxy and 3-oxo-5alpha-androstane steroids controlling the bioavalability of the active forms. Specifically converts dihydrotestosterone to its inactive form 5alpha-androstanediol, that does not bind androgen receptor/AR. Also converts androstanedione, a precursor of testosterone and estrone, to epiandrosterone. Expected to use NAD(+) as preferred electron donor for the 3-beta-hydroxy-steroid dehydrogenase activity and NADPH for the 3-ketosteroid reductase activity.

Pathway

Steroid hormone biosynthesis.

Steroid metabolism.

Sequence Similarities

Belongs to the 3-beta-HSD family.

Tissue Specificity

Steroidogenic tissues (includes testes, ovaries and adrenal glands).

Cellular localization

• Endoplasmic reticulum membrane
• Single-pass membrane protein
• Mitochondrion membrane
• Single-pass membrane protein

Alternative names

Hsd3b, Hsd3b1, 3 beta-hydroxysteroid dehydrogenase/Delta 5-->4-isomerase type 1, 3 beta-hydroxysteroid dehydrogenase/Delta 5-->4-isomerase type I, 3-beta-hydroxy-5-ene steroid dehydrogenase, 3-beta-hydroxy-Delta(5)-steroid dehydrogenase, 3-beta-hydroxysteroid 3-dehydrogenase, Delta-5-3-ketosteroid isomerase, Dihydrotestosterone oxidoreductase, Steroid Delta-isomerase, 3-beta-HSD I

Database links

swissprot:P24815 swissprot:P26150 entrezGene:15494 entrezGene:15492 swissprot:O35469 swissprot:P26149