Return of billions-year-old enzymes shows how photosynthesis has adapted to rise in oxygen science environment

The most widespread enzyme on earth is Rubisco, which serves as the primary biocatalyst in photosynthesis. A group of Max Planck researchers has understood one of the most important adaptations of early photosynthesis by reconstructing enzymes billions of years old. Their results not only shed light on how modern photosynthesis developed, but also provide new ideas for improving it.

Today’s existence depends entirely on CO2 being captured and converted by photosynthetic organisms such as plants and algae. At the heart of these operations is an enzyme called Rubisco, which absorbs more than 400 billion tons of CO2 annually. Rubisco had to continuously adapt to changing environmental conditions in order to be able to occupy such a significant position in the global carbon cycle. A team from the Max Planck Institute for Terrestrial Microbiology in Marburg, in collaboration with the University of Singapore, has now succeeded in reviving and studying billions-year-old enzymes in the laboratory using a combination of computational and synthetic methods. The researchers discovered that in this process, which they call “molecular paleontology,” an entirely new component prepares photosynthesis to adapt to increased oxygen levels, rather than making direct mutations in the active site.

Rubisco’s early confusion Rubisco is very old; it first appeared in early metabolism, some four billion years before oxygen was present on Earth. As oxygen levels in the atmosphere increased and oxygen-producing photosynthesis developed, the enzyme began to catalyze an unintended reaction, mistaking O2 for CO2 and creating compounds that were harmful to cells. This unclear substrate scope still harms Rubiscos today and reduces photosynthetic productivity. Although CO2 specificity increased over time in Rubiscos developing in oxygen-rich environments, none of them were able to completely eliminate the oxygen uptake response.

Which chemical factors contribute to the higher CO2 specificity of Rubisco is still completely unknown. However, those working to improve photosynthesis are very interested in them. It is interesting to note that with higher CO2 specificity, the Rubiscos recruited a brand new protein component with an unidentified function. Although this component has been thought to be responsible for increasing CO2 specificity, it has been difficult to pinpoint the true cause of its origin as it had already evolved over billions of years. Studying evolution by resurrecting ancient proteins in the lab

Researchers from the Max Planck Institute for Terrestrial Microbiology in Marburg and Nanyang Technological University in Singapore used a statistical algorithm to recreate forms of Rubiscos that existed billions of years ago, before oxygen levels began to rise to mark this crucial event in the planet Evolution to understand from more specific Rubiscos. The Max Planck team of Tobias Erb and Georg Hochberg revived these antiquated proteins in the laboratory to study their properties. In particular, the researchers questioned whether the occurrence of increased specificity had anything to do with the new component of Rubisco. The answer was surprising, as PhD student Luca Schulz explains: “We expected that the new component would somehow exclude oxygen directly from the Rubisco catalytic subunit. The subunit altered the effect of subsequent mutations on the Rubisco catalytic subunit. Previously trivial mutations suddenly had a huge impact on specificity when this new component was present. It appears that this new subunit has completely changed the evolutionary potential of Rubisco.”

An enzyme’s dependence on its new subunit This function as an “evolutionary modulator” also explains another mysterious aspect of the new protein component: Rubiscos, which incorporated it, is completely dependent on it, although other forms of Rubisco can function perfectly without it. The same modulating effect explains why: When Rubisco is bound to this small protein component, it becomes tolerant of mutations that would otherwise be catastrophically harmful. With the accumulation of such mutations, Rubisco effectively became addicted to his new subunit.

Taken together, the results provide an explanation as to why Rubisco has retained this novel protein component since its discovery. Georg Hochberg, leader of the Max Planck Research Group, explains: “The fact that this compound was discovered only recently underscores how crucial evolutionary analysis is to understanding the biochemistry that drives the world around us. We can learn so much about why biomolecules like Rubisco are the way they are today by studying their past. Furthermore, we still know very little about the evolutionary history of many biological phenomena. So it’s incredibly interesting to be an evolutionary biochemist at this time because almost the entire molecular history of the cell hasn’t been revealed yet.” Scientific time travel can provide valuable insights for the future

According to Max Planck Director Tobias Erb, the study also has significant implications for how photosynthesis can be improved. “Our research has shown us that previous attempts to improve Rubisco may have been looking in the wrong area. For many years, research was limited to changing the amino acids in Rubisco itself. Our research shows that modifying the enzyme with whole new protein parts possible would be more advantageous and open up previously impassable evolutionary pathways. The field of enzyme engineering is unexplored here.” (ANI)

(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)