How a Tiny Bacterial Enzyme Could Pave the Way for a New Class of Antibiotics

When you think of antibiotics, you probably picture the classic drugs that jam the bacterial ribosome or tear apart cell walls. But metabolism—how bacteria turn food into energy—has always been a tempting, yet tricky, target. That’s why a recent study published by researchers at the University of Heidelberg caught our attention: they’ve discovered a tiny protein that can literally throw a wrench into the production of acetyl‑coenzyme A (acetyl‑CoA), a molecule that sits at the heart of bacterial metabolism.

Acetyl‑CoA is kind of the metabolic Swiss army knife. It links glycolysis to the citric‑acid cycle, fuels fatty‑acid synthesis, and even plays a role in gene regulation. In most living cells, the enzyme acetyl‑CoA synthetase (ACS) stitches together acetate, ATP and coenzyme A to make acetyl‑CoA. The new protein, which the team has named “Acetyl‑CoA Blocker” (AcB), binds to ACS and blocks its active site, preventing the reaction from ever getting off the ground.

“We were looking at a completely different pathway, trying to understand how bacteria survive under nutrient‑starved conditions,” says lead author Dr. Lina Köhler. “Then, almost by accident, we saw that certain strains stopped growing when we knocked out a gene we didn’t even know existed. That gene turned out to encode AcB.”

Using X‑ray crystallography, the researchers visualized AcB perched on ACS like a tiny hand covering a light switch. The binding is highly specific—AcB latches onto a pocket that is present only in bacterial ACS enzymes, leaving the human counterpart untouched. That specificity is crucial because it means any drug designed to mimic AcB could theoretically target bacteria without harming our own cells.

To test whether this interaction could be exploited therapeutically, the team synthesized a small molecule that mimics the key contact points of AcB. In laboratory tests, the compound halted the growth of several pathogenic strains, including Staphylococcus aureus and Pseudomonas aeruginosa, at concentrations that were non‑toxic to human cell cultures.

It’s still early days, but the implications are tantalizing. Antibiotic resistance continues to rise, and the pipeline for new drugs is alarmingly thin. Targeting metabolic choke points—especially ones that are absent in human cells—offers a fresh strategy that could bypass many of the resistance mechanisms bacteria have evolved against traditional drugs.

Of course, challenges remain. The metabolic flexibility of bacteria means they might find alternative routes to produce acetyl‑CoA if this pathway is blocked. Moreover, delivering the inhibitor into the bacterial cell in a clinical setting poses its own set of hurdles.

Still, Dr. Köhler is optimistic: “We’ve opened a door. Now it’s about walking through it, tweaking the chemistry, and seeing if we can turn this basic discovery into a viable antibiotic. It’s a reminder that sometimes, the smallest proteins can have the biggest impact.”