New materials for bio-based hydrogen synthesis; synthetic biology enables spontaneous protein activation
Researchers at the Ruhr-Universität Bochum (RUB) (Germany), with colleagues from the MPI (Max Planck Institute) Mülheim and Université Grenoble, have discovered an efficient process for hydrogen biocatalysis. They developed semi-synthetic hydrogenases—hydrogen-generating enzymes—by adding the protein’s biological precursor to a chemically synthesized inactive iron complex.
From these two components, the biological catalyst formed spontaneously in a test tube, thus greatly simplifying the design and production of hydrogenases. The team reports on their work in a paper in the journal Nature Chemical Biology.
Under ideal conditions, one single hydrogenase enzyme can generate 9,000 hydrogen molecules per second. Nature has created a catalyst that is incredibly active even without any rare noble metals.
Extracting hydrogenases from living cells is highly difficult. Therefore, their industrial application has always been a long way off. Now, we have made a decisive step towards the generation of bio-based materials.—Prof Dr Thomas Happe, head of the work group Photobiotechnology at RUB
The researchers examined iron-iron [FeFe] hydrogenases, the catalysis of which is based on an active center with a complex structure that contains iron, carbon monoxide and cyanide—only few living organisms are able to synthesize it.
In order to skip the inefficient process of hydrogenase production, chemists have recreated the enzyme component that is catalytically active. Even though the reproduction was successful, these mimics—chemical imitations—only generate small volumes of hydrogen.
Due to the difficulty of extracting active hydrogenases from living organisms, Thomas Happe’s team suggested an optimization of the method that had been reported by the research team from Bochum and their collaboration partners in Nature in June 2013. (Berggren et al.)
The RUB biologists mixed the inactive hydrogenase precursor and the inactive chemical mimic, which was synthesized by their colleagues from Grenoble, within a test tube. A few minutes later, a strong generation of H2 was observed. The hydrogenase precursor had spontaneously integrated the chemically synthesized iron substance into its protein scaffold.
Biophysical analyses at the MPI in Mülheim showed that the enzyme thus generated is indistinguishable from natural hydrogenase.
Until now, it has been assumed that enzymes with a complex structure such as hydrogenases require helper proteins to integrate the metal catalyst unit. When I proposed the idea for this experiment for the first time, nobody believed that it could work.—Thomas Happe
Using the bacterium Escherichia coli, the researchers can quickly produce several milligrams of the hydrogenase’s precursor. Subsequently, this is added to the chemical mimic and thence creates fully activated enzymes within a short period of time, said Happe’s PhD student Julian Esselborn.
Because commercial processes for the cultivation of E. coli are already established, industrial application of the new method is within reach, according to the researchers.
Thomas Happe’s research is funded by the Volkswagen Foundation under the title “LigH2t”.
J. Esselborn, C. Lambertz, A. Adamska-Venkatesh, T. Simmons, G. Berggren, J. Noth, J. Siebel, A. Hemschemeier, V. Artero, E. Reijerse, M. Fontecave, W. Lubitz, T. Happe, (2013) Spontaneous activation of [FeFe]-hydrogenases by an inorganic [2Fe] active site mimic, Nature Chemical Biology doi: 10.1038/nchembio.1311
G. Berggren, A. Adamska, C. Lambertz, T. Simmons, J. Esselborn, M. Atta, S. Gambarelli, J.M. Mouesca, E. Reijerse, W. Lubitz, T. Happe, V. Artero, M. Fontecave (2013) Biomimetic assembly and activation of [FeFe]-hydrogenases, Nature doi: 10.1038/nature12239