Characteristics and Kinetics of Iron Releasefrom the Ferritin under the EGCG reduction
Characteristics and Kinetics of Iron Releasefrom the Ferritin under the EGCG reduction
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DOI：
10.1007/s12011-011-9225-4
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发表时间：
2012-04-01
影响因子：
3.9
通讯作者：
Huang, Heqing
中科院分区：
文献类型：
--
作者：
Ji, Xuetao;Huang, Lin;Huang, Heqing
铁蛋白释放铁是体内铁代谢的关键步骤，但其机制尚不清楚。本文分别采用紫外可见光谱、荧光光谱和圆二色性光谱法研究了茶叶中表没食子儿茶素没食子酸酯（表没食子儿茶素没食子酸酯）与黄貂肝铁蛋白（DALF）之间的相互作用强度和结合稳定性。结果表明，在没有Na 2S 2 O 4等化学还原剂存在的情况下，EGCG可以直接还原铁蛋白壳内的铁，但该过程严格依赖于pH值，铁的释放速率在低pH值时比在高pH值时快。它不同于维生素C等化学还原剂的一级反应。此外，还利用荧光光谱和圆二色性光谱进一步研究了铁释放的还原机制，发现在还原过程中，铁蛋白壳层的构象发生了轻微的变化，这是因为DALF-EGCG形成了复合物。看来，具有大分子尺寸的化学还原剂通过电子转移途径（ETP）的方式还原穿过蛋白质壳的铁。一种新的途径，铁释放从DALF与表没食子儿茶素没食子酸酯还原的建议，以解释还原途径的铁代谢的生物还原剂在体内。
The mechanism of iron release from ferritin in vivo is still unclear even though it represents a key step of the metabolism of iron in vivo. Here, both interaction intensity and binding stability between epigallocatechin gallate (EGCG) from tea and liver ferritin of Dasyatis akajei (DALF) were investigated using UV-visible, fluorescence and circular dichroism (CD) spectrometry, respectively. The results indicated that EGCG could reduce the iron within the ferritin shell directly in the absence of chemical reducers such as Na2S2O4, but this process was strictly pH-dependent, and the rate of iron release is faster at low pH than at high pH. The kinetic study of iron release showed that this process fitted the law of zero order reaction, which differed from that of first order reaction by various chemical reducers such as Vitamin C. In addition, Both fluorescence and CD spectrometry were further used to study the reduction mechanism of iron release in vitro, showing that there was a slight conformation change of the ferritin shell during EGCG reduction because of a complex formation of DALF-EGCG. It appears that chemical reducers with large molecular sizes reduce the iron across the protein shell by the way of an electron transfer pathway (ETP). A novel pathway for iron release from DALF with EGCG reduction is suggested to explain for a reductive route of iron metabolism by biological reducers in vivo.