Plate Nº 19 · recorded October 10, 2026
Chemistry & MaterialsReported finding
One-Atom Swap Makes Plastic-Eating Enzymes Nearly Twice as Effective
Australian researchers doubled the efficiency of PET-degrading enzymes by swapping a single carbon for a nitrogen atom, without sacrificing stability.
By Nathan Brooks4 min read715 words
In brief
- A single-atom substitution made PET-degrading enzymes nearly twice as efficient while preserving thermal stability.
- The study, led by Dr. Elwy Abdelkader, was published in Angewandte Chemie International Edition (2026).
- The new PETra fluorescence test measures enzyme activity in minutes instead of hours or days.
- The approach uses noncanonical amino acids called azatryptophans to expand beyond nature's 20 amino acids.
Swapping a single carbon atom for a nitrogen atom nearly doubled the efficiency of plastic-degrading enzymes while leaving their stability intact, researchers at The Australian National University (ANU) report in Angewandte Chemie International Edition.
The enzymes in question break down polyethylene terephthalate, or PET—one of the most widely used plastics in the world, found in drink bottles, food packaging and synthetic fibres. Enzymes capable of degrading PET, known as PET hydrolases or PETases, have already been heavily optimised through computational design and protein engineering. But that optimisation has hit a familiar wall.
Why is improving enzymes so difficult?
Enzyme engineers face a stubborn trade-off: the changes that make a protein more active often make it less stable, and the changes that stabilise it tend to dampen its activity. Lead author Dr. Elwy Abdelkader, from ANU's Research School of Chemistry, described the problem directly.
"Enzymes can be engineered over and over again to improve their performance, but eventually you reach a point where making them more active can also make them less stable, and vice versa," Abdelkader said. "What we have shown is that you can go beyond this limit by making an incredibly precise change—down to a single atom—while largely preserving the structure and stability of the enzyme."
How does a one-atom change work?
The team's technique relies on noncanonical amino acids—building blocks of proteins that do not occur naturally in organisms. Specifically, they used molecules called azatryptophans, which closely mimic the natural amino acid tryptophan except that a carbon-hydrogen group is replaced by a single nitrogen atom.
The researchers inserted this substitution at one precise site in PET-degrading enzymes. The result: the modified enzymes broke down PET nearly twice as efficiently as before, and they retained their thermal stability—the ability to keep working at elevated temperatures, which matters for industrial applications.
The finding challenges a common assumption in the field, according to Abdelkader. "Instead of redesigning an enzyme with many mutations, we can make a very small, targeted change and have a significant effect on how it works," he said.
What is PETra?
Alongside the enzyme work, the team developed a new screening tool called PETra, a rapid fluorescence-based test that measures PET-degrading enzyme activity in minutes rather than the hours or days conventional assays require.
PET itself is insoluble and structurally complex, which makes it slow to assay directly. PETra sidesteps this by using a soluble fluorescent substrate that mimics PET. The researchers showed that PETra results correlate strongly with how effectively enzymes break down solid PET, meaning the test should reliably predict real-world performance and greatly speed up the screening of future enzyme variants.
Could this go beyond plastic recycling?
Co-author Professor Thomas Huber believes the implications reach well past plastic waste. Nature gives protein engineers only 20 amino acids to work with, and azatryptophans sit outside that palette.
"Proteins are incredibly powerful machines, but we are generally limited to the 20 amino acids found in nature when we engineer them," Huber said. "Building on the team's experience with the site-specific introduction of noncanonical amino acids into proteins, we can introduce tiny chemical changes that allow us to tune proteins with a level of precision that was previously difficult to achieve."
The researchers say the same single-atom strategy could potentially be applied to engineer enzymes for a wide range of uses, including sustainable manufacturing, biotechnology and medicine.
What are the caveats?
The findings come from laboratory experiments, and the study demonstrates the principle on PETases specifically. Whether the approach transfers as cleanly to other enzyme classes, or scales to industrial plastic-processing volumes, remains to be tested. The correlation between PETra results and solid-PET degradation, while strong in this study, will also need validation across a broader range of enzyme variants.
Still, the core result is hard to ignore: in a field accustomed to stacking multiple mutations to squeeze out marginal gains, a change invisible to the naked eye—one atom—delivered a near-doubling of efficiency at no apparent cost to stability.
The paper, "Isosteric Engineering of Enzymes: Overcoming Activity–Stability Trade-Offs by Site-Selective CH → N Substitutions," appears in Angewandte Chemie International Edition (2026), DOI: 10.1002/anie.8993497.
via Phys.org Chemistry (Source)
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