Evidence for a one-electron mechanism of 2-aminofluorene oxidation by prostaglandin H synthase and horseradish peroxidase.
Evidence for a one-electron mechanism of 2-aminofluorene oxidation by prostaglandin H synthase and horseradish peroxidase.
复制标题
前列腺素 H 合酶和辣根过氧化物酶氧化 2-氨基芴的单电子机制的证据。
DOI：
10.1016/s0021-9258(18)89829-5
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
T. Eling
中科院分区：
文献类型：
--
作者：
J. Boyd;T. Eling
先前的研究表明，主要芳胺致癌物2-氨基芴（2-AF）被前列腺素H合酶过氧化物酶氧化成能够与大分子共价结合的致突变和亲电子产物。本研究旨在鉴定负责结合的潜在反应性中间体，并进一步表征2-AF过氧化反应中的代谢中间体。前列腺素H合酶和辣根过氧化物酶与H2 O2一起将2-AF氧化为偶氮芴、2-氨基二芴胺（2-ADFA）、2-硝基芴、聚合物和无机可提取物质。这两种酶在pH 5.0下比在pH 7.0下显示更大的活性。在2-叔丁基-4-甲氧基苯酚或2，6-二甲基苯酚的存在下，以高产率形成芳胺/苯酚加合物，其中2-AF或2-ADFA的氮与苯酚的帕拉偶联（与2-叔丁基-4-甲氧基苯酚失去-OCH 3）。这些结构通过质谱和NMR光谱证实。在苯酚的存在下，N-羟基-2-AF的酸水解产生氮鎓离子，也导致加合物的形成，但仅在大于2小时的时间和非常有限的产率。然而，过氧化物酶催化的加合物形成是快速的（小于2分钟）和广泛的。这些和其他数据支持2-AF过氧化的单电子途径，自由基或自由基衍生产物负责与蛋白质和DNA结合。因此，N-羟基中间体可能不是2-AF酶促活化为致突变产物的必要条件。
Previous studies have shown that the primary arylamine carcinogen 2-aminofluorene (2-AF) is oxidized by the prostaglandin H synthase peroxidase to mutagenic and electrophilic products capable of covalent binding to macromolecules. The present study was designed to identify the potential reactive intermediate(s) responsible for binding, and to characterize further the metabolic intermediates in 2-AF peroxidation. Both prostaglandin H synthase and horseradish peroxidase, with H2O2, oxidize 2-AF to azofluorene, 2-aminodifluorenylamine (2-ADFA), 2-nitrofluorene, polymeric and nonorganic-extractable material. Both enzymes show greater activity at pH 5.0 than at pH 7.0. In the presence of either 2-t-butyl-4-methoxyphenol or 2,6-dimethylphenol, arylamine/phenol adducts were formed in high yield, with the nitrogen of either 2-AF or 2-ADFA coupled to the para position of the phenol (loss of -OCH3 with 2-t-butyl-4-methoxyphenol). These structures were confirmed by mass spectrometry and NMR spectroscopy. Acid hydrolysis of N-hydroxy-2-AF to yield the nitrenium ion, in the presence of a phenol, also results in adduct formation, but only at times greater than 2 h and in very limited yield. The peroxidase-catalyzed adduct formation, however is rapid (less than 2 min) and extensive. These and other data support a one-electron pathway for 2-AF peroxidation, with a free radical or a free radical-derived product responsible for binding to protein and DNA. An N-hydroxy intermediate may therefore not be obligatory in the enzymatic activation of 2-AF to a mutagenic product.