Novel evidence of cytochrome P450-catalyzed oxidation of phenanthrene in Phanerochaete chrysosporium under ligninolytic conditions

Abstract

The presence of cytochrome P450 and P450-mediated phenanthrene oxidation in the white rot fungus Phanerochaete chrysosporium under ligninolytic condition was first demonstrated in this study. The carbon monoxide difference spectra indicated induction of P450 (130 pmol mg(-1) in the microsomal fraction) by phenanthrene. The microsomal P450 degraded phenanthrene with a NADPH-dependent activity of 0.44 ± 0.02 min(-1). One of major detectable metabolites of phenanthrene in the ligninolytic cultures and microsomal fractions was identified as phenanthrene trans-9,10-dihydrodiol. Piperonyl butoxide, a P450 inhibitor which had no effect on manganese peroxidase activity, significantly inhibited phenanthrene degradation and the trans-9,10-dihydrodiol formation in both intact cultures and microsomal fractions. Furthermore, phenanthrene was also efficiently degraded by the extracellular fraction with high manganese peroxidase activity. These results indicate important roles of both manganese peroxidase and cytochrome P450 in phenanthrene metabolism by ligninolytic P. chrysosporium.

Genome-to-function characterization of novel fungal P450 monooxygenases oxidizing polycyclic aromatic hydrocarbons (PAHs)

“…The relative abundance of the three phenanthrols was consistent with the regiospecificity profile observed for the whole fungus [1]; 9-phenanthrol was found to be the most abundant whereas 3-phenanthrol the least. In this context, it is interesting that recent whole fungus-based studies using nutrient-limited (defined low nitrogen) cultures showed the formation of a single monohydroxylated product, 9-phenanthrol [17]. In previous PC studies [11], it was unclear whether a single P450 or multiple P450s are involved in the formation of multiple phenanthrols via formation of different epoxides (9, 10-oxide versus 3, 4-oxide).…”

“…Originally, its aromatic ring-oxidizing activity was ascribed to the non-specific extracellular peroxidases [8,9] that are differentially expressed under nutrient-limited (ligninolytic) culture conditions [10]. Subsequent studies by us and others have led to increasing evidences on peroxidase-independent degradation of several aromatics including PAHs under nutrient-sufficient (non-ligninolytic) culture conditions and involvement of P450 monooxygenation reactions [11–17]. Role of P450 monooxygenation in the rate-limiting initial oxidation of HMW PAHs and certain LMW PAHs with high ionization potential (> 7.35 eV) such as phenanthrene has also been reported in other basidiomycete and non-basidiomycete fungi [4,18].…”

Involvement of the Ligninolytic System of White-Rot and Litter-Decomposing Fungi in the Degradation of Polycyclic Aromatic Hydrocarbons

“…Later, the important roles of both cytochrome P-450 and MnP in PHE metabolism by P. chrysosporium were found [55]. Ning et al [55] showed that the microsomal P-450 degraded PHE with a NADPH-dependent activity.…”

“…Ning et al [55] showed that the microsomal P-450 degraded PHE with a NADPH-dependent activity. One of the major detectable metabolites of PHE in the ligninolytic cultures and microsomal fractions was identified as phenanthrene- trans -9,10-dihydrodiol.…”

Degradation of polycyclic aromatic hydrocarbons by newly isolated Curvularia sp. F18, Lentinus sp. S5, and Phanerochaete sp. T20

“…Thus Phanerochaete sp. T20 likely degrades fluorene under nonligninolytic conditions such that it degrades fluorene via cytochrome P450 monooxygenase, as is frequently found with P. chrysosporium and other white-rot fungi 39,48,49 . The three PAH-degrading fungi that were isolated in this study can potentially be used for bioremediation.…”