Protein Engineering a Carbon-Neutral Photorespiration Pathway

Photorespiration is a harmful side-reaction in the carbon fixation cycle, which causes loss of carbon and energy. We have designed a synthetic photorespiration pathway which avoids the loss of carbon, and consumes 30% less energy. When introduced into plants this pathway may improve the overall energy efficiency of carbon fixation by over 10%- potentially leading to faster growth and increased survival in harsh environments. This pathway consists of four novel enzymatic reactions, and we have experimentally identified enzyme candidates for each step. We have used directed evolution to engineer these enzymes to have acceptable rates and specificity for catalysis in vitro and for the eventual realization of the complete pathway in vivo.

This work advances our understanding of metabolic optimality and pathway design principles, and opens up new directions in engineering cellular carbon fixation pathways through directed evolution.