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Appl. Environ. Microbiol., Feb 1996, 593-600, Vol 62, No. 2
SW Kullman and F Matsumura
Recent studies have shown that cultures of white rot fungi not favoring the
production of lignin and manganese peroxidases are effective in degrading
certain xenobiotics. In this study we have used endosulfan as a model
xenobiotic to assess the enzymatic mechanisms of pesticide metabolism under
ligninolytic (nutrient-deficient) and nonligninolytic (nutrient-rich)
culture conditions. Rapid metabolism of this chlorinated pesticide occurred
under each nutrient condition tested. However, the extent of degradation
and the nature of the metabolic products differed for nutrient-deficient
and nutrient-rich media. The pathways for endosulfan metabolism were
characterized by analysis of the fungal metabolites produced. The major
endosulfan metabolites were identified by gas chromatography-electron
capture detection and gas chromatography-mass spectrometry as endosulfan
sulfate, endosulfan diol, endosulfan hydroxyether, and a unknown metabolite
tentatively identified as endosulfan dialdehyde. The nature of the
metabolites formed indicates that this organism utilizes both oxidative and
hydrolytic pathways for metabolism of this pesticide. Piperonyl butoxide, a
known cytochrome P-450 inhibitor, significantly inhibited the oxidation of
endosulfan to endosulfan sulfate and enhanced hydrolysis of endosulfan to
endosulfan diol. We suggest that the metabolism of endosulfan is mediated
by two divergent pathways, one hydrolytic and the other oxidative. Judging
by the inactivity of extracellular fluid and partially purified lignin
peroxidase in metabolizing endosulfan, we conclude that metabolism of this
compound does not involve the action of extracellular peroxidases.
Copyright © 1996, American Society for Microbiology
Metabolic pathways utilized by Phanerochaete chrysosporium for degradation of the cyclodiene pesticide endosulfan
Department of Environmental Toxicology, University of California, Davis 95616, USA.
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