HETEROLOGOUS EXPRESSION OF FUNCTIONALLY ACTIVE HUMAN CYTOCHROMES P450- CYTOCHROME P450IIIA4 CATALYZES CONVERSION OF THE ANABOLIC-STEROID HORMONE METHANDROSTENOLONE

Cytochrome P450IIIA4 has been expression in the yeast Saccharomyces ce revisiae using the pYeDP 1-8/2 shuttle-vector. The microsomal fraction isolated from the transformed yeast was used for conversion of methan drostenolone (MA), an anabolic steroid hormone. The reaction products of the microsomal oxidation were analyzed by HPLC and two-dimensional TLC. Microsomes of the yeast expressing human cytochrome P450IIIA4 cat alyze conversion of MA to its 6 beta-hydroxy derivative. A similar pro duct is formed during the reaction catalyzed by human liver microsomes . Thus, the use of the heterologous system expressing human liver cyto chrome P450IIIA4 established its involvement in the MA metabolism. Thi s system simulates the first phase of conversion of the drug in liver cells.