Osman A M, Posthumus M A, Veeger C, van Bladeren P J, Laane C, Rietjens I M
Department of Biomolecular Sciences, Laboratory of Biochemistry, Agricultural University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
Chem Res Toxicol. 1998 Nov;11(11):1319-25. doi: 10.1021/tx980037l.
This study reports the microperoxidase-8 (MP8)/H2O2-catalyzed dehalogenation of pentafluorophenol and pentachlorophenol, compounds whose toxic effects and persistence in the environment are well documented. The primary products of this dehalogenation reaction appear to be the corresponding tetrahalo-p-benzoquinones. Under the conditions used, the fluorinated phenol and its intermediate products are more susceptible to degradation than the corresponding chlorinated analogue and its products. The main degradation products of tetrachloro-p-benzoquinone and tetrafluoro-p-benzoquinone were identified as trichlorohydroxy-p-benzoquinone and trifluorohydroxy-p-benzoquinone, respectively. This secondary conversion of tetrafluoro-p-benzoquinone and tetrachloro-p-benzoquinone was not mediated by MP8, but was driven by H2O2. Evidence is presented for a mechanism where H2O2 molecules and not hydroxide anions are the reactive nucleophilic species attacking the tetrahalo-p-benzoquinones. In addition to the formation of the trihalohydroxy-p-benzoquinones, the formation of adducts of the tetrahalo-p-benzoquinone products with ethanol, present in the incubation medium, was observed. The adduct from the reaction of tetrachloro-p-benzoquinone with ethanol was isolated and identified as trichloroethoxyquinone. Thus, the present paper describes a system in which the formation of tetrahalo-p-benzoquinone-type products by an oxidative heme-based catalyst could be unequivocally demonstrated.
本研究报道了微过氧化物酶-8（MP8）/H₂O₂催化五氟苯酚和五氯苯酚的脱卤反应，这两种化合物在环境中的毒性效应和持久性已有充分记录。该脱卤反应的主要产物似乎是相应的四卤对苯醌。在所使用的条件下，氟化苯酚及其中间产物比相应的氯化类似物及其产物更易降解。四氯对苯醌和四氟对苯醌的主要降解产物分别被鉴定为三氯羟基对苯醌和三氟羟基对苯醌。四氟对苯醌和四氯对苯醌的这种二次转化不是由MP8介导的，而是由H₂O₂驱动的。有证据表明一种机制，即攻击四卤对苯醌的亲核反应物种是H₂O₂分子而非氢氧根阴离子。除了形成三卤羟基对苯醌外，还观察到四卤对苯醌产物与培养介质中存在的乙醇形成加合物。分离并鉴定了四氯对苯醌与乙醇反应生成的加合物为三氯乙氧基醌。因此，本文描述了一个系统，在该系统中可以明确证明基于血红素的氧化催化剂形成四卤对苯醌型产物的过程。
