Max Planck Institute for Dynamics of Complex Technical Systems, Molecular Simulations and Design Group, Sandtorstrasse 1, 39106 Magdeburg, Germany.
J Am Chem Soc. 2023 May 24;145(20):10954-10959. doi: 10.1021/jacs.3c02438. Epub 2023 May 9.
The oxygen tolerance of the [NiFe]-hydrogenase from was recently assigned to originate from an unusual coordination sphere of the active site nickel atom (Shomura et al. , , 928-932, 10.1126/science.aan4497). In the oxidized state, a terminal cysteine residue is displaced by a bidentate coordinating nearby Glu32 and thus moves to occupy a third μ-cysteine bridging position. Spectral features of the oxidized state were assigned to originate from a closed-shell Ni(IV)/Fe(II) state (Kulka-Peschke et al. , , 17022-17032, 10.1021/jacs.2c06400). Such a high-valent nickel oxidation state is unprecedented in biological systems. The spectral properties and the coordination sphere of that [NiFe]-hydrogenase can, however, also be rationalized by an energetically lower broken-symmetry Ni(III)/Fe(III) state of the active site which was not considered. In this open-shell singlet, the ligand-mediated antiferromagnetic spin-coupling leads to an overall = 0 spin state with evenly distributed spin densities over the metal atoms. Experiments are suggested that may clarify the final assignment of redox states.
最近，来自[NiFe]-氢化酶的氧耐受性被归因于活性位点镍原子的不寻常配位球（Shomura 等人，[]，928-932，10.1126/science.aan4497）。在氧化态下，末端半胱氨酸残基被双齿配位的附近 Glu32 取代，从而移动到占据第三个μ-半胱氨酸桥接位置。氧化态的光谱特征被归因于封闭壳 Ni(IV)/Fe(II)态（Kulka-Peschke 等人，[]，17022-17032，10.1021/jacs.2c06400）。在生物系统中，这种高价镍氧化态是前所未有的。然而，该[NiFe]-氢化酶的光谱性质和配位球也可以通过未考虑的活性位点的能量较低的非对称 Ni(III)/Fe(III)态来合理化。在这种开壳单线态中，配体介导的反铁磁自旋偶合导致整体 = 0 自旋态，金属原子上的自旋密度均匀分布。建议进行实验，以澄清氧化还原态的最终归属。
