Synthetic biology offers the opportunity to build biochemical pathways for the capture and conversion of carbon dioxide (CO2). Researchers at the Max-Planck-Institute for Terrestrial Microbiology have developed a synthetic biochemical cycle that directly converts CO2 into the central building block Acetyl-CoA.
The researchers were able to implement each of the three cycle modules in the bacterium E.coli, which represents a major step towards realizing synthetic CO2 fixing pathways within the context of living cells.
Developing new ways to capture and convert CO2 is key to tackling the climate emergency. Synthetic biology opens avenues for designing new-to-nature CO2-fixation pathways that capture CO2 more efficiently than those developed by nature.
However, realizing those new-to-nature pathways in different in vitro and in vivo systems is still a fundamental challenge. Researchers in Tobias Erb's group have now designed and constructed a new synthetic CO2-fixation pathway, the so-called THETA cycle.
It contains several central metabolites as intermediates and has the central building block, acetyl-CoA, as its output. This characteristic makes it possible to be divided into modules and integrated into the central metabolism of E. coli.
The entire THETA cycle involved 17 biocatalysts and was designed around the two fastest CO2-fixing enzymes known to date: crotonyl-CoA carboxylase/reductase and phosphoenolpyruvate carboxylase.
The researchers found these powerful biocatalysts in bacteria. Although each of the carboxylases can capture CO2 more than ten times faster than RubisCO, the CO2-fixing enzyme in chloroplasts, evolution itself has not brought these capable enzymes together in natural photosynthesis.
The THETA cycle converts two CO2 molecules into one acetyl-CoA in one cycle. Acetyl-CoA is a central metabolite in almost all cellular metabolism and serves as the building block for a wide array of vital biomolecules, including biofuels, biomaterials, and pharmaceuticals, making it a compound of great interest in biotechnological applications. Upon constructing the cycle in test tubes, the researchers could confirm its functionality.
