Covalent Binding of Tea Catechins to Protein Thiols: The Relationship between Stability and Electrophilic Reactivity
Covalent Binding of Tea Catechins to Protein Thiols: The Relationship between Stability and Electrophilic Reactivity
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DOI：
10.1271/bbb.100509
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发表时间：
2010-12-01
影响因子：
1.6
通讯作者：
Nakayama, Tsutomu
中科院分区：
文献类型：
--
作者：
Mori, Taiki;Ishii, Takeshi;Nakayama, Tsutomu
在这项研究中，我们研究了儿茶素的稳定性和它们与蛋白质的亲电反应性之间的关系。通过HPLC分析评价儿茶素的稳定性。儿茶酚型儿茶素在中性缓冲液中稳定，但焦性没食子酚型儿茶素，如（-）-表没食子儿茶素没食子酸酯（EGCg），是不稳定的。儿茶素与模型肽和蛋白质中的硫醇基团的亲电反应性通过质谱和电泳/印迹与氧化还原循环染色来证实。在几种儿茶素的比较中，邻苯三酚型儿茶素比儿茶酚型儿茶素与蛋白质硫醇具有更高的反应性。EGCg的不稳定性和反应性在碱性pH缓冲液中增强。抗氧化剂由于能够防止EGCg自氧化而降低EGCg的反应性。这些结果表明，儿茶素的抗氧化不稳定性与其亲电反应性密切相关。因此，茶儿茶素的这些性质的差异可能有助于其生物活性的大小。
In this study, we investigated the relationship between the stability of catechins and their electrophilic reactivity with proteins. The stability of catechins was evaluated by HPLC analysis. Catechol-type catechins were stable in a neutral buffer, but pyrogallol-type catechins, such as (-)-epigallocatechin gallate (EGCg), were unstable. The electrophilic reactivity of catechins with thiol groups in a model peptide and a protein was confirmed by both mass spectrometry and electrophoresis/blotting with redox-cycling staining. In a comparison of several catechins, pyrogallol-type catechins had higher reactivity with protein thiols than catechol-type catechins. The instability and reactivity of EGCg were enhanced in an alkaline pH buffer. The reactivity of EGCg was reduced by antioxidants due to their ability to prevent EGCg autoxidation. These results indicate that the instability against oxidation of catechins is profoundly related to their electrophilic reactivity. Consequently, the difference in these properties of tea catechins can contribute to the magnitude of their biological activities.