Issue 28, 2024

Oxygen sensitivity of [FeFe]-hydrogenase: a comparative study of active site mimics inside vs. outside the enzyme

Abstract

[FeFe]-hydrogenase is nature's most efficient proton reducing and H2-oxidizing enzyme. However, biotechnological applications are hampered by the O2 sensitivity of this metalloenzyme, and the mechanism of aerobic deactivation is not well understood. Here, we explore the oxygen sensitivity of four mimics of the organometallic active site cofactor of [FeFe]-hydrogenase, [Fe2(adt)(CO)6−x(CN)x]x and [Fe2(pdt)(CO)6−x(CN)x]x (x = 1, 2) as well as the corresponding cofactor variants of the enzyme by means of infrared, Mössbauer, and NMR spectroscopy. Additionally, we describe a straightforward synthetic recipe for the active site precursor complex Fe2(adt)(CO)6. Our data indicate that the aminodithiolate (adt) complex, which is the synthetic precursor of the natural active site cofactor, is most oxygen sensitive. This observation highlights the significance of proton transfer in aerobic deactivation, and supported by DFT calculations facilitates an identification of the responsible reactive oxygen species (ROS). Moreover, we show that the ligand environment of the iron ions critically influences the reactivity with O2 and ROS like superoxide and H2O2 as the oxygen sensitivity increases with the exchange of ligands from CO to CN. The trends in aerobic deactivation observed for the model complexes are in line with the respective enzyme variants. Based on experimental and computational data, a model for the initial reaction of [FeFe]-hydrogenase with O2 is developed. Our study underscores the relevance of model systems in understanding biocatalysis and validates their potential as important tools for elucidating the chemistry of oxygen-induced deactivation of [FeFe]-hydrogenase.

Graphical abstract: Oxygen sensitivity of [FeFe]-hydrogenase: a comparative study of active site mimics inside vs. outside the enzyme

Supplementary files

Article information

Article type
Paper
Submitted
12 Dec 2023
Accepted
25 Jun 2024
First published
26 Jun 2024
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2024,26, 19105-19116

Oxygen sensitivity of [FeFe]-hydrogenase: a comparative study of active site mimics inside vs. outside the enzyme

S. Yadav, R. Haas, E. B. Boydas, M. Roemelt, T. Happe, U. Apfel and S. T. Stripp, Phys. Chem. Chem. Phys., 2024, 26, 19105 DOI: 10.1039/D3CP06048A

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