This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Nearly all metabolic processes require protons—positively charged hydrogen atoms. Although these are abundant in the cellular fluid, the biocatalysts involved depend on mechanisms for efficiently capturing protons and transporting them to the site where catalysis occurs.
Enzymes from microorganisms can produce hydrogen (H₂) by combining electrons with protons. These so-called hydrogenases are so efficient that one biocatalyst can capture nearly 10,000 protons per second. A team of researchers from the Photobiotechnology group at Ruhr University Bochum, Germany, has now discovered how they do this.
The researchers reported their findings in the Journal of the American Chemical Society on Oct. 17, 2026. Zinc occurs naturally in many biocatalysts, where it is needed for the reaction mechanism. This metal ion binds to reactive groups of certain molecular components—the amino acids—of the enzyme.
"Yet through this same bond, zinc can block biocatalysts," explains Dr. Jifu Duan, first author of the current study. "It can also bind nonspecifically to sites required for proton binding." Researchers at Ruhr University Bochum have examined how zinc affects the production of hydrogen by [FeFe]-hydrogenases—and made a discovery.
"Although we were able to see in crystal structures that zinc binds to various sites of the [FeFe]-hydrogenases, the interaction at only one very specific location resulted in inhibition," says Duan. Notably, this point is in the direct vicinity of the previously known proton transport pathway of the hydrogenases. The team working with Duan and professor Thomas Happe was able to demonstrate that the binding of zinc and other metal ions blocks specific amino acids, namely two histidines on the surface of [FeFe]-hydrogenases.
Histidines in enzymes are known for binding protons, but their role in [FeFe]-hydrogenases was previously unexplored. When the researchers replaced one of these histidines with another amino acid, the biocatalyst remained highly active but became insensitive to zinc. However, when they replaced the other histidine, the [FeFe]-hydrogenase could only very slowly produce hydrogen.
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