Oxidation of Fe(II) by flavins under anoxic conditions
Oxidation of Fe(II) by flavins under anoxic conditions
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缺氧条件下黄素对 Fe(II) 的氧化
DOI：
10.1021/acs.est.0c02916
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发表时间：
2020
影响因子：
11.4
通讯作者：
Yuan Songhu
中科院分区：
文献类型：
--
作者：
Zhang Peng;Van Cappellen Philippe;Pi Kunfu;Yuan Songhu
黄素介导的电子传递是异化铁还原菌还原Fe（III）的重要途径。虽然Fe（III）被还原型黄素还原的机理和动力学已被广泛研究，但Fe（II）与氧化型黄素之间的反应很少被研究。本研究的结果表明，在缺氧条件下，Fe（II）可以被氧化形式的核黄素（RBF）和黄素单甘肽（FMN）在pH 7-9的氧化。例如，在pH 9时，17.8 μM Fe（II）在20 min内被10 μM RBF氧化73%。氧化速率和程度均随着氧化黄素浓度的增加和溶液pH的增加而增加。热力学计算和动力学分析表明，Fe（II）的氧化主要通过Fe 2 +-RBF-和Fe 2 +-FMN-复合物的自分解进行，沿着的贡献较小的直接氧化铁（II）的黄素和黄素自由基。我们的研究结果表明，铁（II）氧化黄素的再氧化可能是一个速率控制因素，通过黄素介导的电子转移在微生物Fe（III）还原。
Flavin-mediated electron transfer is an important pathway for Fe(III) reduction by dissimilatory iron-reducing bacteria. Although the mechanisms and kinetics of Fe(III) reduction by reduced flavins have been widely studied, the reaction between Fe(II) and oxidized flavins is rarely investigated. Results of this study show that under anoxic conditions, Fe(II) can be oxidized by the oxidized forms of riboflavin (RBF) and flavin mononucleotide (FMN) at pH 7–9. For instance, at pH 9, 73% of 17.8 μM Fe(II) was oxidized by 10 μM RBF within 20 min. Both the rate and extent of oxidation increased with increasing concentrations of oxidized flavins and increasing solution pH. Thermodynamic calculations and kinetic analyses implied that the oxidation of Fe(II) proceeded predominantly via the autodecomposition of Fe2+–RBF–and Fe2+–FMN–complexes, along with minor contributions from direct oxidation of Fe(II) by flavins and flavin radicals. Our findings suggest that the reoxidation of Fe(II) by oxidized flavins may be a rate-controlling factor in microbial Fe(III) reduction via flavin-mediated electron transfer.