Imma Perfetto
Cosmos science journalist
New Australian research has unravelled a key piece of the carbon fixation process – the conversion of atmospheric carbon dioxide into organic molecules.
In a paper published in Science Advances, researchers from the Australian National University and the University of Newcastle identified the previously unknown function of an enzyme named carboxysomal carbonic anhydrase (CsoSCA).
The enzyme is found in cyanobacteria, or blue-green algae, which are responsible for capturing 12% of the Earth’s CO2 each year through photosynthesis.
The findings have implications for scientists seeking to improve the ability of crops to capture and and using carbon dioxide.
“Unlike plants, cyanobacteria have a carbon dioxide concentrating mechanism (CCM), which allows them to fix carbon from the atmosphere and turn it into sugars at a significantly faster rate than standard plants and crop species,” says first author and PhD researcher Sacha Pulsford, from ANU.
CsoSCA maximises the cyanobacterium’s ability to fix carbon by creating a high local concentration of CO2 inside the CCM. Then, another enzyme, Rubisco, converts it into sugars for the cell to use as energy.
But lead author Dr Ben Long of UoN says that, until now, scientists were unsure how the CsoSCA enzyme is controlled.
“What we found was completely unexpected,” says Long. The process is switched on and off depending on how much of a molecule named RuBP is present.
“When there’s enough, the enzyme is switched on. But if the cell runs out of RuBP, the enzyme is switched off, making the system highly tuned and efficient.”
The findings have implications for biotechnology researchers looking to transplant the bacterial CCM into plant species. This would improve crop yield.
“Understanding how the CCM works not only enriches our knowledge of natural processes fundamental to Earth’s biogeochemistry but may also guide us in creating sustainable solutions to some of the biggest environmental challenges the world is facing,” says Pulsford.
