Evolution of a Non-natural Carboxylase for Synthetic Photorespiration

RuBisCO is the key enzyme of the Calvin cycle, which is the metabolic pathway for most of the carbon fixed in the biosphere. The enzyme shows a side reaction with oxygen (photorespiration) that leads to the production of a toxic intermediate. We propose a completely synthetic photorespiratory bypass. The so-called Tartronyl-CoA bypass circumvents the loss of nitrogen and the release of CO₂, which is a disadvantage in natural photorespiration. We have identified and engineered enzymes that are able to catalyze the required reactions. The key enzyme is a carboxylase that is being engineered towards a reaction with a non-natural substrate.