Human Serum Albumin as an Antioxidant in the Oxidation of (-)-Epigallocatechin Gallate: Participation of Reversible Covalent Binding for Interaction and Stabilization
Human Serum Albumin as an Antioxidant in the Oxidation of (-)-Epigallocatechin Gallate: Participation of Reversible Covalent Binding for Interaction and Stabilization
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DOI：
10.1271/bbb.100600
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发表时间：
2011-01-01
影响因子：
1.6
通讯作者：
Nakayama, Tsutomu
中科院分区：
文献类型：
--
作者：
Ishii, Takeshi;Ichikawa, Tatsuya;Nakayama, Tsutomu
人血清白蛋白 (HSA) 有助于血清中 (-)-表没食子儿茶素没食子酸酯 (EGCg) 的稳定。我们在本研究中描述了 HSA 防止 EGCg 氧化的机制。 EGCg 在人血清或含有 HSA 的缓冲液中稳定，但 (-)-表没食子儿茶素 (EGC) 不稳定。通过在中性缓冲液中比较 EGCg 和 EGC，我们发现 EGCg 比 EGC 具有更高的结合亲和力。这表明没食子酰基部分参与了 EGCg 与 HSA 的相互作用，并且这种相互作用对于防止 EGCg 氧化至关重要。 EGCg 对 HSA 的结合亲和力以及 HSA 中蛋白质羰基的形成在碱性缓冲液中得到增强。这些结果表明，EGCg 通过希夫碱形成进行可逆共价修饰，并且通过形成稳定的复合物将 EGCg 固定到 HSA 上，防止了人血清中 EGCg 的聚合和分解。
Human serum albumin (HSA) contributes to the stabilization of (-)-epigallocatechin gallate (EGCg) in serum. We characterize in the present study the mechanisms for preventing EGCg oxidation by HSA. EGCg was stable in human serum or buffers with HSA, but (-)-epigallocatechin (EGC) was unstable. We show by comparing EGCg and EGC in a neutral buffer that EGCg had a higher binding affinity than EGC. This indicates that the galloyl moiety participated in the interaction of EGCg with HSA and that this interaction was of critical importance in preventing EGCg oxidation. The binding affinity of EGCg for HSA and protein carbonyl formation in HSA were enhanced in an alkaline buffer. These results suggest the reversible covalent modification of EGCg via Schiff-base formation, and that the immobilization of EGCg to HSA, through the formation of a stable complex, prevented the polymerization and decomposition of EGCg in human serum.