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Biological enzymes as a source of hydrogen

Chemists managed to get one step closer to duplicating nature's most efficient mechanism for producing hydrogen gas. This development may help pave the way for the hydrogen fuel industry to play a greater role in the worldwide efforts to achieve more environmentally friendly energy sources.

biological enzymes. Illustration: shutterstock
biological enzymes. Illustration: shutterstock

[Translation by Dr. Nachmani Moshe]

Chemists managed to get one step closer to duplicating nature's most efficient mechanism for producing hydrogen gas. This development may help pave the way for the hydrogen fuel industry to take on a greater role in worldwide efforts to achieve more environmentally friendly energy sources. The research findings have long been published in the scientific journal Proceedings of the National Academy of Sciences.

Today, hydrogen gas is produced through a highly complex industrial process that limits its use in the field of the green fuel market, the researchers say. Therefore, scientists are looking for methods to produce hydrogen biologically, a method that is much more efficient than the process currently done by humans, says the lead researcher.

Biological enzymes that help in the production of hydrogen, called hydrogenases, are the natural mechanism on which the production and consumption of hydrogen gas is based. These enzymes exist in two configurations: iron-iron and iron-nickel, named after the metallic elements responsible for initiating the chemical reactions. The new study focuses on the iron-iron configuration because it makes the reaction faster, the researchers explain. The researchers began their research with a general knowledge of the chemical composition of the active sites within the enzyme.

The researchers hypothesized that these consist of ten parts: four carbon monoxide molecules, two cyanide ions, two iron ions and two groups of a sulfur-containing amino acid called cysteine. The research team discovered that in fact the heart of the enzyme consists of two identical groups each containing five molecules: two molecules of carbon monoxide, one cyanide ion, one iron ion and one group of cysteine. The groups form among themselves one well-tight unit, and the two units are tied together to obtain a finished composition of ten parts. However, the laboratory test of an enzyme synthesized in the laboratory revealed a final surprise, says the lead researcher. "Our recipe was not complete - today we know that the composition contains eleven units and not just ten, and we are now on the hunt for the missing piece."
The research team members are not currently sure what kinds of applications this new insight could give rise to, but the current study could provide a building block that will be useful for other catalyst development projects. "The conclusion from this study is that it is one thing to imagine a real enzyme used to produce hydrogen gas, but on the other hand it is much more complex to understand its composition well enough to reproduce its activity for laboratory use," explains the lead researcher.

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