Unraveling an Ancient Enzyme: A New Frontier in Carbon Capture

Researchers at the University of Illinois Urbana-Champaign have made significant strides in understanding an ancient enzyme known as acetyl-CoA synthase (ACS), which has the potential to revolutionize carbon capture strategies. This enzyme is capable of converting atmospheric carbon dioxide (CO2) and carbon monoxide (CO) into useful biomolecules, a process that could aid in mitigating climate change by transforming greenhouse gases into valuable chemicals. The findings were detailed in a study published in *Nature Communications* on June 27, 2025.

As global CO2 levels continue to rise due to deforestation and fossil fuel consumption, scientists have increasingly turned to ancient biological systems for solutions. This enzyme, which plays a critical role in the Wood-Ljungdahl Pathway (WLP), has puzzled researchers for decades due to the complexity of its mechanism. The final step of this biochemical pathway is facilitated by ACS, which catalyzes the conversion of CO2 and CO into acetyl-CoA, an essential building block for various biomolecules.

According to Dr. Liviu Mirica, a professor of chemistry at the University of Illinois and the lead researcher of the study, the challenge in understanding ACS lies in the fleeting nature of its intermediate species, which are sensitive to oxygen and difficult to characterize. "Each step of the reaction occurs rapidly, making it hard to capture the details of the mechanism," Dr. Mirica explained. "The intermediates involved are short-lived and unstable."

In their groundbreaking research, Mirica and graduate student Shounak Nath developed a synthetic functional model that mimics the behavior of ACS, allowing for a deeper exploration of its catalytic mechanism than previously possible. The researchers focused on isolating and studying key organometallic intermediates, including a rare nickel species known as Ni(methyl)(CO). This synthetic model utilized a special ligand, 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPr3tacn), which effectively slowed down the reaction rate, enabling the researchers to observe these intermediates directly.

Nath, who dedicated three years to the research, presented the findings at the 6th Symposium on Advanced Biological Inorganic Chemistry (SABIC-2024) in Kolkata, India. The response from the scientific community was overwhelmingly positive. "I had the opportunity to present our work to Dr. Steve Ragsdale, a pioneer in the study of ACS, and he expressed excitement about our ability to visualize the Ni(methyl)(CO) intermediate, a long-sought target in the field," Nath noted.

The implications of this research extend beyond academic interest. The insights gained into the ACS mechanism can guide the design of new, efficient catalysts for carbon capture. Dr. Mirica emphasized that the research aligns with industry efforts to develop cheaper, more abundant nickel-based catalysts as alternatives to expensive precious metals like rhodium, which are used in current industrial processes. "There's a significant push in the chemical industry to explore catalytic processes utilizing more abundant and less costly transition metals," he stated.

The potential applications of these findings are vast, particularly in the context of creating sustainable methods for chemical synthesis. By understanding ACS's enzymatic steps, researchers hope to engineer synthetic catalysts that replicate its function, leading to innovations in carbon sequestration technologies.

In conclusion, the work conducted by the team at the University of Illinois not only sheds light on the complexities of an ancient biological system but also holds promise for addressing contemporary environmental challenges. As the world grapples with the effects of climate change, the exploration of natural mechanisms like those exhibited by ACS may provide critical pathways toward a more sustainable future.