Involvement of Cytochrome P450 in Pentachlorophenol Transformation in a White Rot Fungus Phanerochaete chrysosporium

Daliang Ning,Hui Wang,Melanie R Mormile

doi:10.1371/journal.pone.0045887

Abstract

The occurrence of cytochrome P450 and P450-mediated pentachlorophenol oxidation in a white rot fungus Phanerochaete chrysosporium was demonstrated in this study. The carbon monoxide difference spectra indicated induction of P450 (103±13 pmol P450 per mg protein in the microsomal fraction) by pentachlorophenol. The pentachlorophenol oxidation by the microsomal P450 was NADPH-dependent at a rate of 19.0±1.2 pmol min−1 (mg protein)−1, which led to formation of tetrachlorohydroquinone and was significantly inhibited by piperonyl butoxide (a P450 inhibitor). Tetrachlorohydroquinone was also found in the cultures, while the extracellular ligninases which were reported to be involved in tetrachlorohydroquinone formation were undetectable. The formation of tetrachlorohydroquinone was not detectable in the cultures added with either piperonyl butoxide or cycloheximide (an inhibitor of de novo protein synthesis). These results revealed the pentachlorophenol oxidation by induced P450 in the fungus, and it should be the first time that P450-mediated pentachlorophenol oxidation was demonstrated in a microorganism. Furthermore, the addition of the P450 inhibitor to the cultures led to obvious increase of pentachlorophenol, suggesting that the relationship between P450 and pentachlorophenol methylation is worthy of further research.

Highlights

Pentachlorophenol (PCP) has been widely applied for decades around the world, as a fungicide, herbicide, defoliant and detergent supplement in soaps [1]
We proposed significant induction of P. chrysosporium P450 by PCP according to the carbon monoxide (CO) difference spectrum with a peak at 457 nm, and found an increase of PCP degradation with the presence of P450 inhibitor [27]
After concentration of the acetylated extract, the metabolites were analyzed by comparing the GC profiles (Figure 1) with those of acetylated extracts from the control cultures without PCP

Summary

Introduction

Pentachlorophenol (PCP) has been widely applied for decades around the world, as a fungicide (mainly as wood preservative), herbicide, defoliant and detergent supplement in soaps [1]. In addition to obvious acute effects, PCP can cause birth defects, chromosome abnormalities, blood disorders, nerve damage [4], cancer (confirmed in animal and probable in human) [5] and endocrine disruption [6]. Because of such high toxicity and persistence in the environment, there is a complete ban on PCP production within the European Union (EU). The white rot fungi, which can decompose lignin, can effectively transform PCP and were widely studied for the treatment of PCP-contaminated soil [9,10] and wastewater [11]. PCP methylation was found in some bacteria [16], and much more common among fungi including the white rot fungi [1,17]

Methods

Results

Conclusion