Wiese F W, Chang H C, Lloyd R V, Freeman J P, Samokyszyn V M
Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
Arch Environ Contam Toxicol. 1998 Apr;34(3):217-22. doi: 10.1007/s002449900308.
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.
2,4,6-三氯苯酚（TCP）是一种环境污染物，具有毒性、致突变性和致癌性。我们使用辣根过氧化物酶（HRP）作为模型过氧化物酶，研究了过氧化物酶催化的TCP氧化反应，以此作为TCP生物活化的替代途径。结果表明，TCP可作为HRP的还原底物，这一点可通过TCP依赖的、HRP催化的5-苯基-4-戊烯-1-基氢过氧化物（PPHP）还原为相应的醇来证明。此外，通过对反应混合物进行电子吸收光谱分析发现，TCP可发生依赖于氢过氧化物（H2O2、乙基氢过氧化物或PPHP） 的代谢。通过反相高效液相色谱法检测到单一主要产物，并基于电子吸收光谱、质谱以及与合成标准品的共色谱分析，将其鉴定为2,6-二氯-1,4-苯醌（2,6-二氯-2,5-环己二烯-1,4-二酮，CAS编号：697-91-6）。此外，HRP催化的TCP氧化反应产生了电子顺磁共振（EPR）可检测的苯氧自由基中间体，其EPR谱由1:2:1三重峰组成，其质子超精细偶合常数aH(3,5) = 2.35高斯。本文提出了与这些结果一致的、依赖于氢过氧化物的HRP催化TCP氧化反应的机制。
