In a recent study, UniSysCat scientists Marius Horch and Ingo Zebger demonstrated how the catalytic cycle for hydrogen cleavage in a hydrogenase, which is an enzyme that converts molecular hydrogen reversibly to protons and electrons, can be potentially accelerated by irradiation with light. This opens up new ways of manipulating and possibly controlling biocatalytic hydrogen splitting - which is of great interest in view of the use of hydrogen as an energy carrier.
Hydrogenases are a family of enzymes that receive a lot of scientific attention, also within UniSysCat. These enzymes catalyze the reversible oxidation of molecular hydrogen (H2): This way, they can split H2 but also produce it. Consequently, they are very interesting for biotechnological applications, for example for the use as catalysts in biofuel cells. A number of research groups at UniSysCat are therefore working to understand how exactly hydrogenases function and how they can ultimately be controlled for utilization as biotechnological applications, e.g. as bioanodes.
During the chemical reaction of hydrogen cleavage, the structure and redox state of the hydrogenase active site changes. It passes through various intermediate states, which together form the so-called catalytic cycle. The UniSysCat groups of spectroscopists Horch and Zebger are trying to understand this cycle in detail. They now studied the impact of temperature and illumination on an oxygen-resistant and thermostable [NiFe] hydrogenase from the bacterium Hydrogenophilus thermoluteolus using infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy.
They detected an unusual behavior of the [NiFe] hydrogenase: The analysis of the spectroscopic data revealed the direct interconversion of two intermediate states of the hydrogenase, that has not been observed up to now. This behavior represents a potential shortcut of the catalytic cycle that is controlled by light.
The results highlight the diversity of redox-structural states of the studied [NiFe] hydrogenase that can be formed under catalytically relevant conditions and the various thermal and photochemical reaction channels that connect them. It remains to be elucidated, which of these states and transformations are functionally relevant and whether this relevance is conserved across [NiFe] hydrogenases from different classes or organisms. Ultimately, the current findings provide new perspectives for the manipulation of hydrogenases with light.
This study has been published in Angewandte Chemie: Light‐Induced Electron Transfer in a [NiFe] Hydrogenase Opens a Photochemical Shortcut for Catalytic Dihydrogen Cleavage, C. Karafoulidi‐Retsou, C. Lorent, S. Katz, Y. Rippers, H. Matsuura, Y. Higuchi, I. Zebger, M. Horch, Angewandte Chemie International Edition 2024, https://doi.org/10.1002/anie.202409065