An ancient metabolite damage-repair system sustains photosynthesis in plants

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the major catalyst in the conversion of carbon dioxide into organic compounds in photosynthetic organisms. However, its activity is impaired by binding of inhibitory sugars such as xylulose-1,5-bisphosphate (XuBP), which must be detached from the active sites by Rubisco activase. Here, we show that loss of two phosphatases in Arabidopsis thaliana has detrimental effects on plant growth and photosynthesis and that this effect could be reversed by introducing the XuBP phosphatase from Rhodobacter sphaeroides. Biochemical analyses revealed that the plant enzymes specifically dephosphorylate XuBP, thus allowing xylulose-5-phosphate to enter the Calvin-Benson-Bassham cycle. Our findings demonstrate the physiological importance of an ancient metabolite damage-repair system in degradation of by-products of Rubisco, and will impact efforts to optimize carbon fixation in photosynthetic organisms. Rubisco is responsible for sequestering virtually all of the carbon dioxide in the global carbon cycle. Here, the authors demonstrate that two conserved phosphatases degrade Rubisco misfire products that inhibit photosynthesis in plants.

Automated summary

In this study, it was found that the activity of Rubisco, the major catalyst in carbon dioxide conversion, is impaired by inhibitory sugars. The loss of two phosphatases in plants negatively affects plant growth and photosynthesis, but this effect can be reversed by introducing a XuBP phosphatase from Rhodobacter sphaeroides. This finding demonstrates the physiological importance of a metabolite damage-repair system in degradation of Rubisco by-products and has implications for carbon fixation optimization in photosynthetic organisms.