Miller Effie K, Trivelas Nicholas E, Maugeri Pearson T, Blaesi Elizabeth J, Shafaat Hannah S
Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Biochemistry. 2017 Jul 5;56(26):3369-3379. doi: 10.1021/acs.biochem.7b00403. Epub 2017 Jun 16.
The assembly mechanism of the Mn/Fe ligand-binding oxidases (R2lox), a family of proteins that are homologous to the nonheme diiron carboxylate enzymes, has been investigated using time-resolved techniques. Multiple heterobimetallic intermediates that exhibit unique spectral features, including visible absorption bands and exceptionally broad electron paramagnetic resonance signatures, are observed through optical and magnetic resonance spectroscopies. On the basis of comparison to known diiron species and model compounds, the spectra have been attributed to (μ-peroxo)-Mn/Fe and high-valent Mn/Fe species. Global spectral analysis coupled with isotopic substitution and kinetic modeling reveals elementary rate constants for the assembly of Mn/Fe R2lox under aerobic conditions. A complete reaction mechanism for cofactor maturation that is consistent with experimental data has been developed. These results suggest that the Mn/Fe cofactor can perform direct C-H bond abstraction, demonstrating the potential for potent chemical reactivity that remains unexplored.
锰/铁配体结合氧化酶（R2lox）是一类与非血红素二价铁羧酸盐酶同源的蛋白质，其组装机制已通过时间分辨技术进行了研究。通过光学和磁共振光谱观察到多个具有独特光谱特征的异双核中间体，包括可见吸收带和异常宽的电子顺磁共振信号。基于与已知二价铁物种和模型化合物的比较，这些光谱被归因于（μ-过氧）-锰/铁和高价锰/铁物种。全局光谱分析结合同位素取代和动力学建模揭示了有氧条件下锰/铁R2lox组装的基本速率常数。已经建立了一个与实验数据一致的辅因子成熟的完整反应机制。这些结果表明，锰/铁辅因子可以直接进行C-H键的提取，证明了其潜在的强大化学反应性，而这一点尚未得到探索。
