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Appl. Environ. Microbiol., Jul 1996, 2547-2553, Vol 62, No. 7
L Bezalel, Y Hadar, PP Fu, JP Freeman and CE Cerniglia
The white rot fungus Pleurotus ostreatus, grown for 11 days in
basidiomycetes rich medium containing [14C] phenanthrene, metabolized 94%
of the phenanthrene added. Of the total radioactivity, 3% was oxidized to
CO2. Approximately 52% of phenanthrene was metabolized to
trans-9,10-dihydroxy-9,10-dihydrophenanthrene (phenanthrene trans-9,10-
dihydrodiol) (28%), 2,2'-diphenic acid (17%), and unidentified metabolites
(7%). Nonextractable metabolites accounted for 35% of the total
radioactivity. The metabolites were extracted with ethyl acetate, separated
by reversed-phase high-performance liquid chromatography, and characterized
by 1H nuclear magnetic resonance, mass spectrometry, and UV spectroscopy
analyses. 18O2-labeling experiments indicated that one atom of oxygen was
incorporated into the phenanthrene trans-9,10- dihydrodiol. Circular
dichroism spectra of the phenanthrene trans-9,10- dihydrodiol indicated
that the absolute configuration of the predominant enantiomer was 9R,10R,
which is different from that of the principal enantiomer produced by
Phanerochaete chrysosporium. Significantly less phenanthrene
trans-9,10-dihydrodiol was observed in incubations with the cytochrome
P-450 inhibitor SKF 525-A (77% decrease), 1-aminobenzotriazole (83%
decrease), or fluoxetine (63% decrease). These experiments with cytochrome
P-450 inhibitors and 18O2 labeling and the formation of phenanthrene
trans-9R,10R-dihydrodiol as the predominant metabolite suggest that P.
ostreatus initially oxidizes phenanthrene stereoselectively by a cytochrome
P-450 monoxygenase and that this is followed by epoxide hydrolase-catalyzed
hydration reactions.
Copyright © 1996, American Society for Microbiology
Metabolism of phenanthrene by the white rot fungus Pleurotus ostreatus
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel.
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