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Issue 1, 2014
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Inaccessibility of the μ-hydride species in [FeFe] hydrogenases

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[FeFe] hydrogenases catalyse the reversible formation and oxidation of H2. They presumably feature a hydride species as a key intermediate. The H ligand can either be bound between the iron atoms of the [2Fe]H subsite (μ-H) or terminally to the distal iron atom of the active site (terminal-H). Although the μ-H species is thermodynamically most stable, experimental evidence points to the terminal-H species as the relevant intermediate. In order to understand these contradictory results, we investigate the catalytic cycle of [FeFe] hydrogenases (including transition states) with a special focus on the role of the two possible hydride intermediates. For this, density functional theory calculations were carried out for a large quantum mechanical active-site model. It is shown that formation of the μ-H intermediate is prohibited by high activation barriers which are caused by interactions of the H cluster with surrounding amino acids. We provide direct evidence for the anchoring of the H cluster in the protein to be decisive for the kinetic hindrance of μ-H formation.

Graphical abstract: Inaccessibility of the μ-hydride species in [FeFe] hydrogenases

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The article was received on 19 Jun 2013, accepted on 16 Sep 2013 and first published on 20 Sep 2013

Article type: Edge Article
DOI: 10.1039/C3SC51700D
Chem. Sci., 2014,5, 215-221

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    Inaccessibility of the μ-hydride species in [FeFe] hydrogenases

    A. R. Finkelmann, M. T. Stiebritz and M. Reiher, Chem. Sci., 2014, 5, 215
    DOI: 10.1039/C3SC51700D

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