Strategies Towards Capturing Nitrogenase Substrates and Intermediates via Controlled Alteration of Electron Fluxes
Strategies Towards Capturing Nitrogenase Substrates and Intermediates via Controlled Alteration of Electron Fluxes
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DOI：
10.1002/chem.201803735
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发表时间：
2019-02-18
影响因子：
4.3
通讯作者：
Hu, Yilin
中科院分区：
文献类型：
--
作者：
Hiller, Caleb J.;Lee, Chi Chung;Hu, Yilin
固氮酶利用ATP依赖性还原酶将电子传递到其催化组分，以实现两个重要的反应：将N-2还原为NH 4+，以及将CO还原为烃。这两种基于固氮酶的反应平行于工业哈伯-博施和费-托工艺，但它们发生在环境条件下。因此，了解固氮酶的酶促机制是至关重要的未来发展的仿生策略的能源效率生产有价值的化学商品。固氮酶反应机理的研究一直受到底物和中间产物捕获困难的限制。最近，我们通过两种方法成功地将CO捕获在棕色固氮菌V-固氮酶上，以可控的方式改变电子通量：一种方法利用人工电子供体将CO捕获在静止状态的V-固氮酶催化组分上;而另一种采用错配的还原酶组分来减少通过系统的电子通量，从而在V-催化组分上积累CO。固氮酶在这里，我们总结了这些最新研究的主要成果，这不仅澄清了固氮酶的一个CO（lo-CO）和多CO（hi-CO）的结合状态的催化相关性，但也指出了潜在的竞争N-2和CO之间的结合到同一对反应性的Fe网站整个辅因子的硫带。总之，这些结果突出了这些策略的效用在poising的辅因子在一个明确定义的状态，通过控制改变电子通量的底物或中间体捕获，这可能被证明是有益的进一步阐明固氮酶催化反应的机理细节。
Nitrogenase utilizes an ATP-dependent reductase to deliver electrons to its catalytic component to enable two important reactions: the reduction of N-2 to NH4+, and the reduction of CO to hydrocarbons. The two nitrogenase-based reactions parallel the industrial Haber-Bosch and Fischer-Tropsch processes, yet they occur under ambient conditions. As such, understanding the enzymatic mechanism of nitrogenase is crucial for the future development of biomimetic strategies for energy-efficient production of valuable chemical commodities. Mechanistic investigations of nitrogenase has long been hampered by the difficulty to trap substrates and intermediates relevant to the nitrogenase reactions. Recently, we have successfully captured CO on the Azotobacter vinelandii V-nitrogenase via two approaches that alter the electron fluxes in a controlled manner: one approach utilizes an artificial electron donor to trap CO on the catalytic component of V-nitrogenase in the resting state; whereas the other employs a mismatched reductase component to reduce the electron flux through the system and consequently accumulate CO on the catalytic component of V-nitrogenase. Here we summarize the major outcome of these recent studies, which not only clarified the catalytic relevance of the one-CO (lo-CO) and multi-CO (hi-CO) bound states of nitrogenase, but also pointed to a potential competition between N-2 and CO for binding to the same pair of reactive Fe sites across the sulfur belt of the cofactor. Together, these results highlight the utility of these strategies in poising the cofactor at a well-defined state for substrate- or intermediate-trapping via controlled alteration of electron fluxes, which could prove beneficial for further elucidation of the mechanistic details of nitrogenase-catalyzed reactions.