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Chemistry and Biology in Synergy - Studies of hydrogenases using a combination of synthetic chemistry and biological tools

Periodic Reporting for period 3 - CaBiS (Chemistry and Biology in Synergy - Studies of hydrogenases using a combination of synthetic chemistry and biological tools )

Reporting period: 2020-02-01 to 2021-07-31

Renewable hydrogen fuel has for many years put been forth as the ultimate clean energy carrier. If produced from solar or wind power it would diminish the world's dependence on coal, oil and gas, thus tackling the challenge of global warming. Still, the question remains on how to produce hydrogen on large-scale with methods that are both environmentally friendly and economically viable. Traditional electrochemical production from water is generally expensive and rely on scarce and expensive noble metals. Despite these drawbacks, facilities employing such technologies are currently being successfully employed in e.g. Norway and Germany, underscoring that this technology is on the rise. However, in order to enable a future global-scale hydrogen society new methods for hydrogen gas production needs to be developed. Remarkably, evolution has already developed an efficient hydrogen economy, in which the production and utilization of hydrogen gas is handled by enzymes called hydrogenases. These biological catalysts operate with efficiencies on par with current state-of-the-art manmade systems without any dependence on precious or rare metals. Consequently, hydrogenases can be employed either for the production of hydrogen gas as a biofuel using genetically modified microorganisms, or alternatively, the isolated enzyme can be incorporated into devices similar to current platinum based technologies. Still, a number of challenges remain before these biological catalysts can be implemented in a technological context, as we still do not fully understand how they function or how we can optimize them for our needs. In this project we are currently addressing these questions using a combination of biology and chemistry techniques. In short, the project is expected to provide unprecedented insight into both the assembly and function of these remarkable enzymes. Moreover, our unusual interdisciplinary approach allows us to develop new methods for working with, and manipulating, not only hydrogenases but also other metalloenzymes.
I have previously developed a method by which a hydrogenase can be activated using man-made synthetic mimics of its catalytic cofactor, resulting in artificial, or “cyborg”, enzymes. In this project we are now further exploring the potential of this approach. Key results so far can be summarized as follows:
1) We have verified that it is possible to introduce synthetic components into the assembly line of the catalytic cofactor, and that these synthetic building blocks are practically indistinguishable from their natural, biological, counterparts. This paves the way for more detailed studies of this so-far incompletely understood process.
2) We have shown that we can take advantage of biological tools for the construction of a new class of completely synthetic miniaturized hydrogenases. These small molecule systems represent a new promising class of manmade catalysts for hydrogen gas production.
3) We have developed techniques for generating artificial enzymes inside living organisms, using a combination of molecular biology and synthetic chemistry tools. This has allowed us to generate fully functional artificial enzymes in both E. coli and different cyanobacteria, thereby improving their hydrogen gas production.
4) We have utilized our unique competence in constructing artificial hydrogenases inside living cells to perform spectroscopic/mechanistic studies of FeFe hydrogenase in vivo.
The concept of preparing artificial enzymes through the introduction of a synthetic complex into a suitable protein host was developed in the late 1970’s by Whitesides. This has allowed the preparation of new classes of catalysts combining the strengths of synthetic chemistry and biology. More recently, I adapted this approach also for hydrogenases. However, this type of chemistry is generally restricted to in vitro studies in test tubes. The techniques developed in this project will enable us to take this chemistry into living organisms. We expect this project to provide hitherto unprecedented insight into the mechanism of hydrogenases, and greatly facilitate their applications in a biotechnological context. In a wider context, it will also enable completely new ways of manipulating and optimizing the metabolism of microorganisms.
Conceptual figure outling the formation of an artificial enzyme inside E. coli