It is now generally accepted that dehydroepiandrosterone (DHA) is one of the androgens secreted by the human adrenal gland and that it arises from the side-chain cleavage of 17α-hydroxypregnenolone (Soloman, Carter & Lieberman, 1960; Gaul, Lemus, Kline, Gut & Dorfman, 1962; Deshpande, Jensen, Carson, Bulbrook & Doouss, 1970; Jones, Groom & Griffiths, 1970). Although the biosynthetic pathways by which the hormone is synthesized have been established, the precise requirements for the side-chain cleavage of 17α-hydroxypregnenolone and the factors affecting the reaction are as yet unknown. For this reason examination of the kinetics of the enzyme involved in the side-chain cleavage of 17α-hydroxypregnenolone (17-desomolase) was undertaken.
Human adrenal glands, obtained at operation from patients with advanced breast cancer, were fractionated in a Beckman Ultra Centrifuge (Model L2–65B) according to the procedure of Allfrey, Littan & Mursky (1964). Tritiated 17α-hydroxypregnenolone (sp.act. 19·9 Ci/mm) used as substrate and [14C]DHA (sp.act. 57·1