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Cobamide-mediated enzymatic reductive dehalogenation via long-range electron transfer.
Nature Communications ( IF 14.7 ) Pub Date : 2017-07-03 , DOI: 10.1038/ncomms15858
Cindy Kunze , Martin Bommer , Wilfred R. Hagen , Marie Uksa , Holger Dobbek , Torsten Schubert , Gabriele Diekert

The capacity of metal-containing porphyrinoids to mediate reductive dehalogenation is implemented in cobamide-containing reductive dehalogenases (RDases), which serve as terminal reductases in organohalide-respiring microbes. RDases allow for the exploitation of halogenated compounds as electron acceptors. Their reaction mechanism is under debate. Here we report on substrate-enzyme interactions in a tetrachloroethene RDase (PceA) that also converts aryl halides. The shape of PceA's highly apolar active site directs binding of bromophenols at some distance from the cobalt and with the hydroxyl substituent towards the metal. A close cobalt-substrate interaction is not observed by electron paramagnetic resonance spectroscopy. Nonetheless, a halogen substituent para to the hydroxyl group is reductively eliminated and the path of the leaving halide is traced in the structure. Based on these findings, an enzymatic mechanism relying on a long-range electron transfer is concluded, which is without parallel in vitamin B12-dependent biochemistry and represents an effective mode of RDase catalysis.

中文翻译:

钴酰胺介导的酶还原性脱卤作用,通过远程电子转移实现。

含金属卟啉类化合物介导还原性脱卤化氢的能力在含钴酰胺的还原性脱卤化酶(RDases)中得到实现,RDases在呼吸有机卤化物的微生物中充当末端还原酶。RDase允许将卤代化合物用作电子受体。他们的反应机制仍在争论中。在这里,我们报告了四氯乙烯RDase(PceA)中的底物-酶相互作用,该酶也可转换芳基卤化物。PceA的高度非极性活性位点的形状指导溴酚在距钴一定距离处且与羟基取代基结合而朝向金属结合。电子顺磁共振光谱未观察到紧密的钴-底物相互作用。尽管如此,羟基对位的卤素取代基被还原消除,并且在结构中描绘了卤化物的残留路径。基于这些发现,可以得出一种依赖于长距离电子转移的酶机制,这在维生素B中是无可比拟的。12-依赖的生物化学,并且代表RDase催化的有效模式。
更新日期:2017-07-03
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