Cholestenone 5 alpha-Reductase (5α-reductase)

Cholestenone 5 alpha-reductase is an oxidoreductase enzyme that catalyzes the conversion of 3-oxo-delta4 steroids into their corresponding 5alpha form. This reaction is crucial in steroid metabolism, particularly in the transformation of testosterone to dihydrotestosterone (DHT) and progesterone to dihydroprogesterone. The enzyme plays a significant physiological role in androgen and estrogen metabolism, as well as bile acid biosynthesis. Inhibitors targeting this enzyme class (e.g., finasteride, dutasteride) are used clinically for benign prostatic hyperplasia and androgenetic alopecia. Deficiency can result in ambiguous genitalia or undervirilization due to insufficient DHT production during fetal development; this condition is known as “five-alpha reductase deficiency”.

Other names

Testosterone Delta4–5alpha-reductaseSteroid 5alpha-reductase3-Oxosteroid Delta4-dehydrogenaseTestosterone Delta4-hydrogenaseCholest-4-en-3-one 5alpha-reductase3-oxo-5alpha-steroid:NADP+ Delta4-oxidoreductaseSteroid/androgenic/Cholestenone-type reductases

Inhibition of 5 alpha-reductase, leading to decreased DHT production