Djurdjevic Ivana, Trncik Christian, Rohde Michael, Gies Jakob, Grunau Katharina, Schneider Florian, Andrade Susana L A, Einsle Oliver
Met Ions Life Sci. 2020 Mar 23;20. doi: 10.1515/9783110589757-014.
In biological nitrogen fixation, the enzyme nitrogenase mediates the reductive cleavage of the stable triple bond of gaseous N2at ambient conditions, driven by the hydrolysis of ATP, to yield bioavailable ammonium (NH4+). At the core of nitrogenase is a complex, ironsulfur based cofactor that in most variants of the enzyme contains an additional, apical heterometal (Mo or V), an organic homocitrate ligand coordinated to this heterometal, and a unique, interstitial carbide. Recent years have witnessed fundamental advances in our understanding of the atomic and electronic structure of the nitrogenase cofactor. Spectroscopic studies have succeeded in trapping and identifying reaction intermediates and several inhibitor- or intermediate- bound structures of the cofactors were characterized by high-resolution X-ray crystallography. Here we summarize the current state of understanding of the cofactors of the nitrogenase enzymes, their interplay in electron transfer and in the six-electron reduction of nitrogen to ammonium and the actual theoretical and experimental conclusion on how this challenging chemistry is achieved.
在生物固氮过程中，固氮酶在ATP水解的驱动下，于环境条件下介导气态N₂稳定三键的还原裂解，生成可被生物利用的铵（NH₄⁺）。固氮酶的核心是一种基于铁硫的复杂辅因子，在该酶的大多数变体中，它含有一个额外的顶端杂金属（钼或钒）、一个与该杂金属配位的有机高柠檬酸配体以及一个独特的间隙碳化物。近年来，我们对固氮酶辅因子的原子和电子结构的理解取得了根本性进展。光谱研究成功捕获并鉴定了反应中间体，并且通过高分辨率X射线晶体学对几种抑制剂或中间体结合的辅因子结构进行了表征。在此，我们总结了目前对固氮酶辅因子的理解现状、它们在电子转移以及将氮六电子还原为铵过程中的相互作用，以及关于如何实现这一具有挑战性的化学反应的实际理论和实验结论。
