Hydrogenases in sulfate-reducing bacteria function as chromium reductase
Hydrogenases in sulfate-reducing bacteria function as chromium reductase
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DOI：
10.1007/s00253-003-1390-8
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发表时间：
2003-12-01
影响因子：
5
通讯作者：
Bruschi, M
中科院分区：
文献类型：
--
作者：
Chardin, B;Giudici-Orticoni, MT;Bruschi, M
研究了硫酸盐还原细菌(SRB)还原六价铬的能力，为其在污染环境净化中的应用奠定了基础。金属还原既可以通过细菌产生的硫化氢在化学上实现，也可以在酶作用下通过多氢细胞色素c(3)实现。我们证明，除了低潜势多血红素c型细胞色素外，从硫化弧菌和硫化微生物属SRB分离的[Fe]、[NiFe]和[NiFeSe]氢酶中普遍存在还原铬酸盐的能力。其中，普通硫弧菌Hildenborough菌株的[Fe]氢酶对六价铬的还原速率最高。[Fe]和[NiFeSe]酶对六价铬的K-m相同，说明六价铬还原速率与氢耗速率直接相关。电子顺磁共振光谱使我们能够探测到[NiFe]和[Fe]氢酶中不同金属中心被铬(VI)氧化的情况。这些实验表明，铬(VI)被还原为顺磁性的铬(III)，并在高铬(VI)浓度下对酶有抑制作用。在缺乏[Fe]氢酶的突变株中，氢酶和铬(VI)还原酶的活性都显著降低，这表明该酶参与了体内铬(VI)的还原。用脱硫弧菌的[3Fe-4S]铁氧还蛋白进行的实验表明，低氧化还原的[Fe-S](非血红素铁)簇参与了氢酶还原金属的机理。
The ability of sulfate-reducing bacteria (SRB) to reduce chromate VI has been studied for possible application to the decontamination of polluted environments. Metal reduction can be achieved both chemically, by H2S produced by the bacteria, and enzymatically, by polyhemic cytochromes c(3). We demonstrate that, in addition to low potential polyheme c-type cytochromes, the ability to reduce chromate is widespread among [Fe], [NiFe], and [NiFeSe] hydrogenases isolated from SRB of the genera Desulfovibrio and Desulfomicrobium. Among them, the [Fe] hydrogenase from Desulfovibrio vulgaris strain Hildenborough reduces Cr(VI) with the highest rate. Both [Fe] and [NiFeSe] enzymes exhibit the same K-m towards Cr(VI), suggesting that Cr(VI) reduction rates are directly correlated with hydrogen consumption rates. Electron paramagnetic resonance spectroscopy enabled us to probe the oxidation by Cr(VI) of the various metal centers in both [NiFe] and [Fe] hydrogenases. These experiments showed that Cr(VI) is reduced to paramagnetic Cr(III), and revealed inhibition of the enzyme at high Cr(VI) concentrations. The significant decrease of both hydrogenase and Cr(VI)-reductase activities in a mutant lacking [Fe] hydrogenase demonstrated the involvement of this enzyme in Cr(VI) reduction in vivo. Experiments with [3Fe-4S] ferredoxin from Desulfovibrio gigas demonstrated that the low redox [Fe-S] (non-heme iron) clusters are involved in the mechanism of metal reduction by hydrogenases.