REDUCTIVE ADDITION OF GLUTATHIONE TO PARA-BENZOQUINONE, 2-HYDROXY-PARA-BENZOQUINONE, AND PARA-BENZOQUINONE EPOXIDES - EFFECT OF THE HYDROXY AND GLUTATHIONYL SUBSTITUENTS ON PARA-BENZOHYDROQUINONE AUTOXIDATION
REDUCTIVE ADDITION OF GLUTATHIONE TO PARA-BENZOQUINONE, 2-HYDROXY-PARA-BENZOQUINONE, AND PARA-BENZOQUINONE EPOXIDES - EFFECT OF THE HYDROXY AND GLUTATHIONYL SUBSTITUENTS ON PARA-BENZOHYDROQUINONE AUTOXIDATION
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DOI：
10.1016/0009-2797(88)90021-x
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发表时间：
1988-01-01
影响因子：
5.1
通讯作者：
CADENAS, E
中科院分区：
文献类型：
--
作者：
BRUNMARK, A;CADENAS, E
研究了GSH与不同甲基取代度的对苯醌、2-羟基对苯醌和2，3-环氧对苯醌的还原加成反应，考察了它们的吸收光谱变化和自氧化反应。GSH与对苯醌的亲核加成产生在λ 303 nm处具有最大吸收的谷胱甘肽-对苯醌产物。该化合物缓慢自氧化-但速率比母体氢醌高8倍-生成谷胱甘肽-对苯醌，其在λ 367 nm处显示最大吸收。谷胱甘肽衍生物的自氧化伴随着O2消耗和H2 O2形成。GSH与2-羟基-对苯醌或2，3-环氧-对苯醌的亲核加成产生相同的主要分子产物，2-羟基-5-谷胱甘肽基-对苯醌，该化合物在λ 300 nm处显示最大吸收，并且以比缺少1/2 OH取代基的母体谷胱甘肽基对苯二酚高得多的速率（44倍）自氧化。自氧化产物2-羟基-5-戊二酰-对苯醌在λ 343 nm处显示出最大吸光度以及在较长波长（λ 520 nm）处显示出分辨的吸收带，后者由sbdOH取代基贡献。谷胱甘肽取代基在醌的还原电位中仅产生微小的变化，而在水溶液中测得的半波还原电位，sbd.OH取代基显著降低。如下所示的两种取代基均显著提高了自氧化速率：羟基-谷胱甘肽-对苯并氢醌. mchgt。羟基对苯并氢醌谷胱甘肽-对苯并对苯二酚>对苯并对苯二酚。超氧化物歧化酶提高了对苯并氢醌及其谷胱甘肽加合物的自氧化速率，而它抑制了有或无谷胱甘肽取代的羟基衍生物的自氧化。这些结果的生物化学意义根据GSH还原性加成到对-苯醌上的助氧化剂特性进行了讨论，羟基醌和醌环氧化物。
The reductive addition of GSH to p-benzoquinones, 2-hydroxy-p-benzo-quinone, and 2,3-epoxy-p-benzoquinones with different degree of methyl substitution was studied in terms of absorption spectral changes and autoxidation reactions. The nucleophilic addition of GSH to p-benzoquinone yields a glutathionyl-p-benzohyroquinone product with maximal absorption at .lambda.303 nm. This compound autoxidizes slowly - but at a rate 8-fold higher than the parent hydroquinone - to glutathionyl-p-benzoquinone, which reveals maximal absorption at .lambda.367 nm. The autoxidation of the glutathionyl derivative is accompanied by O2 consumption and H2O2 formation. The nucleophilic addition of GSH to either 2-hydroxy-p-benzoquinone or 2,3-epoxy-p-benzoquinone yields the same primary molecular product, 2-hydroxy-5-glutationyl-p-benzohydroquinone, a compound that shows maximal absorption at .lambda.300 nm and autoxidizes at rates substantially higher (44-fold) than the parent glutathionylhydroquinone lacking a .sbd.OH substituent. The autoxidation product, 2-hydroxy-5-glutationyl-p-benzoquinone, reveals maximal absorbance at .lambda.343 nm as well as a resolved absorption band at longer wavelengths (.lambda.520 nm), the latter contributed by the .sbd.OH substituent. The glutathionyl substituent exerted only minor changes in the reduction potential of the quinones, whereas the .sbd.OH substituent lowered significantly the half-wave reduction potential, as measured in aqueous solutions. The rate of autoxidation was markedly enhanced by both substituents as follows: hydroxy-glutathionyl-p-benzohydroquinone .mchgt. hydroxy-p-benzohydroquinone .mchgt. glutathionyl-p-benzohydroquinone > p-benzohydroquinone. Superoxide dismutase enhanced the rate of autoxidation of p-benzohydroquinone and its glutationyl adduct, whereas it inhibited autoxidation of the hydroxy derivatives with or without glutathionyl substitution. The biochemical significance of these results is discussed in terms of the pro-oxidant character of the reductive addition of GSH to p-benzoquinones, .alpha.-hydroxyquinones, and quinone epoxides.