Peroxidase-Catalyzed Oxidation of 2,4,6-Trichlorophenol |
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Authors: | F W Wiese H C Chang R V Lloyd J P Freeman V M Samokyszyn |
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Institution: | (1) Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA , US;(2) National Center for Toxicological Research, Food and Drug Administration, Jefferson, Arkansas 72079, USA , US;(3) Department of Chemistry, University of Memphis, Memphis, Tennessee 38152, USA , US |
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Abstract: | 2,4,6-Trichlorophenol (TCP) is an environmental contaminant that is toxic, mutagenic, and carcinogenic. We have investigated
peroxidase-catalyzed oxidation of TCP as an alternative pathway of TCP bioactivation using horseradish peroxidase (HRP) as
a model peroxidase. TCP was shown to function as a reducing substarte for HRP as evidenced by TCP-dependent, HRP-catalyzed
reduction of 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) to its corresponding alcohol. In addition, TCP was shown to undergo
hydroperoxide (H2O2, ethyl hydroperoxide, or PPHP)-dependent metabolism as evidenced by electronic absorption spectroscopic analysis of reaction
mixtures. A single major product was detected by reverse phase HPLC and was identified as 2,6-dichloro-1,4-benzoquinone (2,6-dichloro-2,5-cyclohexadiene-1,4-dione,
CAS no. 697-91-6) on the basis of electronic absorption spectroscopy, mass spectrometry, and cochromatography with synthetic
standard. In addition, HRP-catalyzed oxidation of TCP yielded EPR-detectable phenoxyl radical intermediates whose EPR spectrum
consisted of a 1:2:1 triplet characterized by proton hyperfine coupling constants aH(3,5)= 2.35 gauss. Mechanisms for the hydroperoxide-dependent, HRP-catalyzed oxidation of TCP are proposed that are consistent
with these results.
Received: 9 August 1997/Accepted: 5 October 1997 |
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