THE ROLE OF CYTOCHROME P450(11-ALPHA) IN DETOXIFICATION OF STEROIDS IN THE FILAMENTOUS FUNGUS RHIZOPUS NIGRICANS

The evidence was presented that steroid hydroxylating enzyme complex i nduced by substrate in the filamentous fungus Rhizopus nigricans (R. n igricans) alleviated toxic effect(s) of the steroid on fungal growth. The growth inhibition of fungal mycelium observed in steroid-containin g culture(s) became much more obvious when fungal mycelia were grown i n the simultaneous presence of inducing steroid and the P450(11 alpha) inhibitor metyrapone. One the other hand, in experiments where we fol lowed the fate of radioactively labelled progesterone added to the myc elial suspension, we noticed that steroid, after being initially accum ulated in the microorganism, was, after some time, released from it; t he latter phenomenon was not observed if induction of 11 alpha-hydroxy lase was prevented by cycloheximide. Results of experiments presented in this communication can be regarded as the first strong indication t hat the biological role of P450(11 alpha) induction in R. nigricans is in removal of steroids which are toxic for the mycelium.