Eagle Eye Magazine Issue 1 2023

“Research has shown how to create
hydrogenases for cleaner, accessible
energy sources.
ENZYMES INTO
ELECTRICITY?
Photo: iStock.com/Arthon Meekodong
Recent graduate Jack Badley (Molecular and Cellular Biochemistry,
2018) was part of a research team whose findings were recently
published in top journal Nature. The team discovered an enzyme that
converts air into energy.
Analysis of a hydrogen-consuming enzyme from a
common soil bacterium showed that it used low
amounts of hydrogen in the atmosphere to create an
electrical current. Here, Jack tells us more about the
remarkable discovery and the role he played on the team.
What started the research group thinking about the possibility
of using an enzyme from common soil bacterium to convert
air into energy?
Hydrogenases are enzymes which reversibly convert molecular
hydrogen into protons and electrons. These generated electrons
can be utilised by cells to produce energy, similar to how we
derive energy from glucose. Initially discovered in the 1930s,
hydrogenases and hydrogenase-containing bacteria have been
an invaluable resource for multiple biotechnological fields for
some time. These include wastewater management, hydrogen
production from cheap substrates like glucose, the direct
production of clean and reproducible electricity from hydrogen via
enzymatic biofuel cells, as well as cheaper and more eco-friendly
methods to produce biologically active compounds like medicines.
Despite the number of biotechnological processes that rely
on these enzymes, there has been a significant challenge in
utilising hydrogenases effectively. These enzymes evolved in
an era when the Earth’s atmosphere had significantly higher
hydrogen levels and very little oxygen. These two gas molecules
are very similar in terms of shape, size, and charge meaning most
enzymes have little means to separate them, which is a concern
as oxygen is capable of binding to the same metal centre that
normally converts hydrogen, but for a significantly longer period.
Sometimes this even produces bi-product like hydrogen peroxide
which can permanently damage the protein. Consequently,
modern hydrogenases are extremely sensitive to oxygen inhibition,
reducing or even halting their efficiency when exposed to air,
significantly hindering their practical application.
Since their discovery almost 90 years ago, countless research
groups have been working hard to modify or discover
hydrogenases that could function quickly and efficiently in
atmospheric conditions, while maintaining the ability to
specifically bind hydrogen strongly enough to source it from the
extremely low atmospheric concentration. However, while great
improvements were made, the level of discrimination between
oxygen and hydrogen required to function efficiently when
exposed to air was not able to come close to existing within
any characterised lineage or variant of hydrogenase. However,
in recent years, several high-affinity hydrogenase lineages have
been discovered that show remarkable functionality in aerobic
conditions with near-immunity to oxygen inhibition, efficiently
converting hydrogen even at concentrations lower than those in
our current atmosphere.
Importantly, up until this project, no such oxygen-tolerant
hydrogenase had been successfully isolated, making our group the
first to successfully resolve one of their structures, which is vital
in understanding how this immunity to oxygen is achieved for
future study and the production of more efficient hydrogenasebased
biotech. Grinter et al. successfully resolved the structure of
Huc Hydrogenase from M. smegmatis, to a resolution which at the
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