SIDEROPHORE ELECTROCHEMISTRY - RELATION TO INTRACELLULAR IRON RELEASE MECHANISM
SIDEROPHORE ELECTROCHEMISTRY - RELATION TO INTRACELLULAR IRON RELEASE MECHANISM
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DOI：
10.1073/pnas.75.8.3551
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发表时间：
1978-01-01
影响因子：
11.1
通讯作者：
RAYMOND, KN
中科院分区：
文献类型：
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作者：
COOPER, SR;MCARDLE, JV;RAYMOND, KN
先前的研究表明，肠杆菌素（一种基于儿茶酚的铁载体）的铁释放机制与基于异羟肟酸盐的铁载体（如铁色素）的铁释放机制之间存在重大差异。对于铁肠杆菌素，存在在Fe释放期间水解配体的酯酶。铁被释放的异羟肟酸盐为基础的铁载体和配体在随后的铁运输中被重新使用。异羟肟酸盐通过还原成亚铁络合物释放Fe，这是铁肠杆菌素不会发生的过程。在生理还原剂范围内，铁色素A和铁胺B的循环伏安图显示可逆的1电子波，其形式电位（Ef与正常H电极）分别为-446和-454 mV。铁肠杆菌素也显示出可逆的1-电子波（pH > 10），Ef = -986 mV，与正常H电极相比。根据该电位的pH依赖性，估计在pH 7下的还原电位为-750 mV。与异羟肟酸铁的值形成鲜明对比，该值远低于生理还原剂的范围。结果表明，所观察到的肠杆菌素的水解是通过三价铁离子还原从铁载体体内释放铁的必要先决条件。
Previous studies showed that there is a major difference between the Fe release mechanism of enterobactin, a catechol-based siderophore, and that of the hydroxamate-based siderophores such as ferrichrome. For ferric enterobactin there is an esterase that hydrolyzes the ligand during Fe release. Fe is released by the hydroxamate-based siderophores and the ligands are reused in subsequent Fe transport. Release of Fe by hydroxamates occurs by reduction to the ferrous complex, a process that does not occur for ferric enterobactin. Cyclic voltammograms of ferrichrome A and ferrioxamine B exhibit reversible 1-electron waves with pH-independent formal potentials (Ef vs. the normal H electrode)-446 and -454 mV, respectively, within the range of physiological reductants. Ferric enterobactin also shows a reversible 1-electron wave (at pH > 10) with Ef = -986 mV vs. the normal H electrode. From the pH dependence of this potential, a reduction potential of -750 mV at pH 7 was estimated. In sharp contrast to the value for the ferric hydroxamates, this value is well below the range of physiological reducing agents. The results demonstrate that the observed hydrolysis of enterobactin is a necessary prerequisite to in vivo release of iron from the siderophore via ferric ion reduction.