3 beta-hydroxysteroid dehydrogenase/Delta 5-->4-isomerase type 1 (HSD3B1)

A bifunctional enzyme responsible for the oxidation and isomerization of 3beta-hydroxy-Delta(5)-steroid precursors to 3- oxo-Delta(4)-steroids, an important step in steroid hormone biosynthesis. Specifically catalyzes the conversion of pregnenolone to progesterone, 17alpha-hydroxypregnenolone into 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.