Components of the Cytochrome P-450 Monooxygenase System of the Fungus,Fusarium oxysporum: Conditions for Induction and Isolation of Cytochromeb5

Abstract

Not only cytochrome P-450 but also cytochrome E5-like hemeproteins, NADPH-cytochrome c reductase, and N ADH-ferricyanide reductase activities could be detected in the cell-free extract of a cytochrome P-450-producing fungus, Fusarium oxysporum. Both cytochromes (P-450 and b5) could be reduced anaerobically with a natural reductant (NADPH or NADH), suggesting the existence of an electron transport system to reduce the cytochromes. Further, two monooxygenase activities, i.e., N- demethylase and benzo[a]pyrene monooxygenase, were also found in the extract in addition to the fatty acid hydroxylase previously found. These components and activities seemed to be induced concomitantly. One of the cytochrome E5-like hemeproteins was isolated, the absorption spectra and molecular weight (Mr = 16,200) of which closely resembled those of hepatic cytochrome b5 of mammals. From these results we concluded that this fungus has a cytochrome P-450-containing electron transport system similar to that in hepatic microsomes of mammals in addition to the unique nitrate/nitrite-inducible cytochrome P-450 system previously found.