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Combining Spectroscopy and Theory to Evaluate Structural Models of Metalloenzymes: A Case Study on the Soluble [NiFe] Hydrogenase from Ralstonia eutropha

Authors

  • Marius Horch,

    Corresponding author
    1. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
    • Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
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  • Yvonne Rippers,

    1. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
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  • Prof. Maria A. Mroginski,

    1. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
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  • Prof. Peter Hildebrandt,

    1. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
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  • Dr. Ingo Zebger

    Corresponding author
    1. Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
    • Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany), Fax: (+49) 30-314-21122
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Abstract

Hydrogenases catalyse the reversible cleavage of molecular hydrogen into protons and electrons. While most of these enzymes are inhibited under aerobic conditions, some hydrogenases are catalytically active even at ambient oxygen levels. In particular, the soluble [NiFe] hydrogenase from Ralstonia eutropha H16 couples reversible hydrogen cycling to the redox conversion of NAD(H). Its insensitivity towards oxygen has been formerly ascribed to the putative presence of additional cyanide ligands at the active site, which has been, however, discussed controversially. Based on quantum chemical calculations of model compounds, we demonstrate that spectroscopic consequences of the proposed non-standard set of inorganic ligands are in contradiction to the underlying experimental findings. In this way, the previous model for structure and function of this soluble hydrogenase is disproved on a fundamental level, thereby highlighting the efficiency of computational methods for the evaluation of experimentally derived mechanistic proposals.

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