Penicillin has been saving lives since the 1940s, yet scientists still had not seen exactly how nature builds it. A new study led by the University of Oxford has now filmed the process. Using ultrafast X-ray pulses, the team made a frame-by-frame “molecular movie” that shows how penicillin is made inside an enzyme. The work was published in Nature Catalysis.
Why the penicillin ring matters
Penicillin and its relatives are called β-lactam antibiotics. Their power comes from a strained, ring-shaped chemical structure called the β-lactam ring. This ring interferes with how bacteria build their cell walls, so the wall eventually fails and the bacteria die.
In nature, an enzyme called isopenicillin N synthase, or IPNS, builds this ring system from a simple chain-like starting molecule. Researchers have studied it for decades, but the key in-between steps happen so fast that nobody could catch them directly. According to Oxford, the study resolves a question about the mechanism that had stayed open for more than four decades.
How the molecular movie was made
Most enzyme pictures are still snapshots, like one photo of a moving car. This team wanted the whole journey. Working with Diamond Light Source, Lawrence Berkeley National Laboratory, PAL-XFEL and SLAC National Accelerator Laboratory, they used X-ray free-electron lasers (XFELs).
- Thousands of tiny droplets containing enzyme microcrystals were placed on a moving tape 2 mm wide.
- The tape passed into an oxygen-filled chamber. Oxygen soaked into the crystals and started the reaction.
- By controlling the tape speed, the team set how long each crystal reacted before an ultrafast X-ray pulse took an atomic-level snapshot.
- Thousands of these snapshots were combined into the movie.
What they saw
The team caught several short-lived stages. One is a thioaldehyde intermediate that forms just before the β-lactam ring is created. Another is a single-ring β-lactam intermediate, the first ring-shaped structure on the way to the full penicillin scaffold. They also found that water molecules inside the enzyme help guide the reaction, and that small movements across the enzyme work together with its chemistry.
“By capturing these fleeting steps, we can better understand how enzymes control complex chemistry with remarkable precision,” said Professor Christopher Schofield, a senior author. First author Dr Patrick Rabe said that understanding the process in atomic detail lets scientists “begin to think about engineering these enzymes to produce new or improved antibiotic scaffolds.”
The bigger worry: antimicrobial resistance
This matters because bacteria are learning to survive our medicines. Oxford notes that one in six bacterial infections is now resistant to antibiotics, and too few new antibiotics are in development. Resistance threatens progress in areas like cancer care and transplant surgery, and puts pressure on health systems and food production.
It’s worth being clear about what this study is and isn’t. It is basic science about how one enzyme works. It does not produce a new antibiotic, and the researchers talk about future possibilities, not ready treatments. Turning these insights into new medicines would take much more work. IPNS also belongs to a large family of iron-dependent enzymes, including ones that help our bodies sense oxygen, so the lessons may reach beyond antibiotics.
Why this matters
As a writer, I think there’s something lovely about a story that goes back to penicillin, a drug most of us have taken without a second thought, and finds that we still didn’t fully understand it. I also want to be careful not to overhype it. A clearer picture of an enzyme is a step, not a cure for drug-resistant infections. But when resistance keeps rising and the medicine pipeline looks thin, I’d rather see scientists going back to basics like this than not. You can decide how hopeful that makes you.
For more on the fight against resistant bacteria, read about IISc’s cow gut enzyme that breaks down tough biofilms and how tiny bacterial vesicles could shape cancer treatment.