Inducibility of cytochrome P-450 and of NADPH-cytochrome C reductase in progesterone treated filamenteous fungi Rhizopus nigricans and Rhizopus arrhizus

Abstract

The inducibility of the enzymes involved in the 11α-hydroxylation of progesterone was studied in filamentous fungi Rhizopus nigricans and Rhizopus arrhizus. We showed that besides the cytochrome P-450, the NADPH cytochrome-C reductase is another component of this steroidal monooxygenase system. The inducibility of cytochrome P-450 and of the reductase was followed by measuring the level of both enzymes during the induction of the hydroxylase in the fungal mycelia with progesterone; neither cytochrome P-450 nor the reductase were present in measurable amounts in the noninduced fungi, whereas the level of both enzymes increased in parallel during the induction. The induction kinetics of the hydroxylase in the intact mycelia is very similar to the induction kinetics of the individual enzymes which was followed in the cell free preparations. It is concluded that the 11α-hydroxylation of progesterone in R. nigricans and R. arrhizus requires the induction, both, of cytochrome P-450 and of NADPH cytochrome-C reductase.