Unlocking photosynthesis potential: Replacing RuBisCO with PEPC to boost crop efficiency
image: Reactions of the MOG cycle are outlined in yellow, reactions of the β-hydroxyaspartate cycle are outlined in blue.
Credit: The authors
This substitution, combined with the development of a new metabolic cycle, the MOG cycle, could potentially revolutionize carbon fixation processes, greatly enhancing plant productivity. The shift promises to optimize photosynthesis, offering future applications in agricultural productivity and climate resilience.
Photosynthesis is the process by which plants convert sunlight into chemical energy, driving the production of biomass. However, its efficiency remains low, primarily due to the limitations of RuBisCO, the enzyme responsible for fixing carbon dioxide. Researchers have explored various strategies to increase photosynthesis efficiency, including optimizing RuBisCO’s function, but the enzyme’s inherent inefficiencies present a substantial challenge. This review delves into how replacing RuBisCO with PEPC, an enzyme with superior kinetic properties, could improve the process, especially when paired with engineered metabolic cycles.
A review (DOI:10.1016/j.bidere.2025.100006) published in BioDesign Research on 26 February 2025 by Viktor Melnik, Vavilov Institute of General Genetics Russian Academy of Sciences, outlines how replacing RuBisCO with phosphoenolpyruvate carboxylase (PEPC) and introducing a new metabolic cycle—dubbed the MOG cycle—could dramatically enhance photosynthetic efficiency.
The research focuses on the inherent inefficiencies of RuBisCO, which is essential for photosynthesis but suffers from slow activity and a tendency to bind oxygen instead of carbon dioxide. These issues reduce photosynthetic efficiency, contributing to substantial energy losses in plants. The proposed solution centers on PEPC, an enzyme with a much higher turnover rate than RuBisCO and no affinity for oxygen, which would bypass some of the limitations of RuBisCO. The challenge lies in the fact that while PEPC is already used in C4 and CAM plants for carbon fixation, no plants naturally replace RuBisCO entirely with PEPC. The primary obstacle is the lack of a metabolic cycle to regenerate the substrate for PEPC, a gap that the research team aims to bridge with the development of the MOG cycle. This cycle, based on malonyl-CoA, oxaloacetate, and glyoxylate, could enable PEPC to function as the sole carbon-fixing enzyme by supplying it with its substrate in a way that mimics natural processes. However, as the MOG cycle produces glyoxalic acid, its integration into plant metabolism presents challenges, notably in terms of toxicity and efficiency. Additionally, the review suggests the potential benefits of combining the MOG cycle with the NOG cycle, which could further enhance carbon fixation, especially during the night, a time when CO2 absorption typically slows in plants. By leveraging nighttime carbon fixation, plants could maximize their productivity. However, creating a fully functional MOG-NOG system would require precise regulation of metabolic fluxes, fine-tuning gene expression, and managing the balance between metabolic pathways.
The shift from RuBisCO to PEPC represents an ambitious leap forward in photosynthesis efficiency. Though there are significant hurdles in regulating metabolic flux and ensuring substrate regeneration, the integration of the MOG cycle into plants could ultimately redefine agricultural productivity and carbon capture. If successfully implemented, plants engineered with the MOG-NOG system could exhibit vastly improved photosynthetic efficiency, leading to higher crop yields and enhanced resilience to climate change. Moreover, this research opens the door to new avenues in bioengineering, potentially paving the way for better carbon capture systems in plants, which could contribute to global efforts in combating climate change.
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References
DOI
Original Source URL
https://doi.org/10.1016/j.bidere.2025.100006
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