Evidence for an 4-Ene-3-oxosteroid-5^-reductase and Δ4-Δ5-Ketosteroid Isomerase Activity in Extracts of Streptomyces hydrogenans

Abstract

Abstract A homogenate of cells of Streptomyces hydrogenans which have been cultivated in the presence of estradiol-17β, was separated by gel filtration on Sephadex G-200. In the presence of NADH, a few distinct fractions converted about 10% of [3H] testosterone to 5α-dihydrotestosterone (5α-DHT), 5α-androstanedione, 4-androstenedione, and dehydroepiandrosterone (DHEA). The metabolites were separated after two consecutive runs on silica gel and propanediol-1,2-impregnated cellulose plates by thin layer chromatography. Identification was achieved by comparison with known steroid samples, specific staining procedures and by crystallization to constant specific radioactivity. The 5α-reductase activity responsible for the formation of 5α-DHT and 5α-androstanedione in vitro required NADH as co-substrate and could only be found after induction of the cells with estradiol-17β in vivo. Within the same chromatographic fractions, a Δ4-Δ5-ketosteroid isomerase activity can be detected which catalyzes the reverse reaction from the 4-androstene testosterone to the 5-anthrostene DHEA in vitro.