Proton Transfer in the Catalytic Cycle of [NiFe] Hydrogenases: Insight from Vibrational Spectroscopy.
Proton Transfer in the Catalytic Cycle of [NiFe] Hydrogenases: Insight from Vibrational Spectroscopy.
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DOI：
10.1021/acscatal.6b03182
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发表时间：
2017-04-07
期刊：
影响因子：
12.9
通讯作者：
Vincent KA
中科院分区：
文献类型：
--
作者：
Ash PA;Hidalgo R;Vincent KA
在以氢气为清洁燃料的可再生能源系统中，催化氢气生产和氧化反应是至关重要的，但目前对铂基催化剂的依赖是不可持续的。在自然界中，H2在氢化酶的[NiFe]催化位点以最小的过电位和高的周转频率被氧化。虽然已经建立了[NiFe]氢化酶的大致机制，包括H2的异裂裂解，然后是第一次和第二次质子和电子从活性位点转移，但关于质子转移如何被靠近活性位点的蛋白质环境促进的细节仍然不清楚。此外，尽管来自不同生物体或细胞环境的[NiFe]氢化酶共享一个共同的活性位点，但它们表现出广泛的催化特性，表明周围蛋白质的细微变化对控制其行为的重要性。本文综述了近年来在电催化转化过程中进行的时间分辨红外光谱研究和原位红外光谱电化学研究。此外，我们重新评估了通过更传统的溶液研究确定的氢化酶活性位点状态的大量红外光谱数据，以突出似乎普遍适用于[NiFe]氢化酶的机制步骤，以及迄今为止似乎仅限于这些酶的特定组的步骤。这一分析旨在帮助将注意力集中在关键的开放性问题上，这些问题需要进一步的工作来评估[NiFe]氢化酶机制中质子和电子转移的重要方面。
Catalysis of H2 production and oxidation reactions is critical in renewable energy systems based around H2 as a clean fuel, but the present reliance on platinum-based catalysts is not sustainable. In nature, H2 is oxidized at minimal overpotential and high turnover frequencies at [NiFe] catalytic sites in hydrogenase enzymes. Although an outline mechanism has been established for the [NiFe] hydrogenases involving heterolytic cleavage of H2 followed by a first and then second transfer of a proton and electron away from the active site, details remain vague concerning how the proton transfers are facilitated by the protein environment close to the active site. Furthermore, although [NiFe] hydrogenases from different organisms or cellular environments share a common active site, they exhibit a broad range of catalytic characteristics indicating the importance of subtle changes in the surrounding protein in controlling their behavior. Here we review recent time-resolved infrared (IR) spectroscopic studies and IR spectroelectrochemical studies carried out in situ during electrocatalytic turnover. Additionally, we re-evaluate the significant body of IR spectroscopic data on hydrogenase active site states determined through more conventional solution studies, in order to highlight mechanistic steps that seem to apply generally across the [NiFe] hydrogenases, as well as steps which so far seem limited to specific groups of these enzymes. This analysis is intended to help focus attention on the key open questions where further work is needed to assess important aspects of proton and electron transfer in the mechanism of [NiFe] hydrogenases.