We demonstrated that more than half of the reverse Krebs cycle can run in water without enzymes driven by metallic Fe and catalyzed by the metal ions Zn2+ and Cr3+ (Muchowska et al. Nature Ecology and Evolution 2017). Next, we showed that two simple metabolites react in iron-rich warm water to recreate many of the reactions of the biological Krebs cycle and glyoxylate cycles (Muchowska et al. Nature 2019).
The discoveries described above led us to develop a non-enzymatic version of another biological CO2-fixation pathway that is thought to be ancient, the Acetyl CoA pathway (also known as the Wood-Ljungdahl pathway). We found that metallic iron, and several other zero-valent metals, fix CO2 on their surface to give the intermediates and end-products of that pathway even at room temperature and ambient pressure (Varma et al. Nature Ecology and Evolution 2018). Later, we found that the biological pathway can be mimicked even more closely using hydrogen gas as the source of electrons and common iron-based minerals as catalysts (Preiner et al. Nature Ecology and Evolution 2020). These discoveries are key for understanding the origin of biological carbon fixation (and the origin of life) because it means that forming C-C bonds from CO2 is not as difficult as previously thought and could have happened before enzymes existed. It is also very important because it shows a direct connection between the most ancient known biological CO2 fixation pathway and prebiotic chemistry.
Taken together, these discoveries have important implications for the origin of life, because it means that these central biological pathways might have started before enzymes existed.
