Hydrogenases can convert hydrogen just as efficiently as expensive platinum catalysts. These are naturally occurring enzymes, for example in green algae, that can both catalytically produce hydrogen and split hydrogen. The actual chemical reaction takes place “at the active center deep inside the enzyme,” explains Oliver Lampret from the photobiotechnology working group at the Ruhr University in Bochum (RUB): “The electrons and protons required for the reaction must therefore have an efficient route there find."
The electrons are transported, so to speak, via an electrical wire that consists of several iron-sulfur clusters. The protons are transported to the active site via a proton transfer pathway consisting of five amino acids and a water molecule. “It was known that there was a proton-coupled electron transfer mechanism, but until now researchers had assumed that the coupling only took place at the active site itself,” says Thomas Happe, head of the Photobiotechnology working group.
The team of scientists from the Ruhr University Bochum and the University of Oxford manipulated the hydrogenases so that the proton transfer became significantly slower, but hydrogen could still be converted, according to a statement. Using dynamic electrochemistry, the researchers showed that hydrogen turnover decreased significantly and that overvoltages were also necessary to catalyze the production or decomposition of hydrogen. “By manipulating the proton transfer path, the researchers indirectly reduced the rate of electron transfer.”
Since the two transfer routes are spatially separated from each other, “we assume that a cooperative long-distance coupling of both processes is necessary for efficient catalysis,” summarizes Oliver Lampret. The findings should contribute to the development of more efficient miniaturized hydrogenase catalysts.
The work was supported by the German Research Foundation and the Volkswagen Foundation.
Oliver Lampret et al.: The roles of long-range proton coupled electron transfer in the directionality and efficiency of [FeFe]-hydrogenases, in: Proceedings of the National Academy of Sciences, 2020, DOI: 10.1073/pnas.2007090117
Photos:
Bochum researchers have gained new insights into the function of hydrogen-producing enzymes. / © RUB, Marquard
