Solomon Edward I, Goudarzi Serra, Sutherlin Kyle D
Department of Chemistry, Stanford University , Stanford, California 94305, United States.
SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
Biochemistry. 2016 Nov 22;55(46):6363-6374. doi: 10.1021/acs.biochem.6b00635. Epub 2016 Nov 14.
The non-heme Fe enzymes are ubiquitous in nature and perform a wide range of functions involving O activation. These had been difficult to study relative to heme enzymes; however, spectroscopic methods that provide significant insight into the correlation of structure with function have now been developed. This Current Topics article summarizes both the molecular mechanism these enzymes use to control O activation in the presence of cosubstrates and the oxygen intermediates these reactions generate. Three types of O activation are observed. First, non-heme reactivity is shown to be different from heme chemistry where a low-spin Fe-OOH non-heme intermediate directly reacts with substrate. Also, two subclasses of non-heme Fe enzymes generate high-spin Fe═O intermediates that provide both σ and π frontier molecular orbitals that can control selectivity. Finally, for several subclasses of non-heme Fe enzymes, binding of the substrate to the Fe site leads to the one-electron reductive activation of O to an Fe-superoxide capable of H atom abstraction and electrophilic attack.
非血红素铁酶在自然界中广泛存在，执行着涉及氧活化的多种功能。相对于血红素酶而言，这些酶一直难以研究；然而，目前已经开发出了能深入了解结构与功能相关性的光谱方法。这篇《当前话题》文章总结了这些酶在共底物存在下控制氧活化所采用的分子机制，以及这些反应生成的氧中间体。观察到三种类型的氧活化。首先，非血红素反应性被证明不同于血红素化学，在血红素化学中，低自旋铁-过氧羟基非血红素中间体直接与底物反应。此外，非血红素铁酶的两个亚类会生成高自旋铁═氧中间体，这些中间体提供了既能控制选择性的σ前沿分子轨道，也能控制选择性的π前沿分子轨道。最后，对于非血红素铁酶的几个亚类，底物与铁位点的结合会导致氧单电子还原活化为能够夺取氢原子和亲电攻击的铁超氧化物。
