A new assay and solubilization procedure for steroid 17,20-lyase from rat testes

We report an assay for testicular 17,20-lyase which depends on the use of [21-14C]progesterone as a substrate. The method is made possible by a simplified procedure for the synthesis of [21-14C]progesterone. A chromatographic separation of the unreacted substrate and the 2-carbon by-product on mini silica gel columns permitted a quantitative assay of the lyase activity. The lyase complex from rat testes has been solubilized by treatment with Triton CF-54 detergent. The solubilized enzyme complex catalyzes the formation of androstenedione (4-androstene-3,17-dione) from progesterone without equilibrium with added 17-hydroxyprogesterone and the solubilized enzyme complex responds to the presence of cytosol activator. Both of these characteristics are similar to the properties of the intact microsomes. Thus, solubilization with this detergent preserves the special properties of the microsome bound enzyme complex.