3-beta hydroxysteroid dehydrogenase/isomerase The enzyme 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) catalyses the oxidation and isomerisation of 5-ene-3 beta-hydroxypregnene and 5-ene-hydroxyandrostene steroid precursors into the corresponding 4-ene-ketosteroids necessaryfor the formation of all classes of steroid hormones.3Beta_HSD