Biophysics Lecture

Carbon fixation is the main pathway for storing energy and accumulating biomass in the living world. It is also the main reason for humanity s usage of land and water resources. Under human cultivation, where water, light and nutrients can be abundant, it is the rate of carbon fixation that significantly limits growth. Hence increasing the rate of carbon fixation is of major importance in the path towards agricultural and energetic sustainability. Are there design principles that limit the rate of such central metabolic pathways? Recent attempts to improve the rate and specificity of Rubisco, the key enzyme in the Calvin-Benson cycle, have achieved only limited improvement. In this lecture we consider options to overcome this bottleneck by systematically exploring the space of carbon fixation pathways that can be assembled from all ~4000 metabolic enzymes known in nature. We computationally compare all possible metabolic pathways based on kinetics, energetics and topology. Our initial analysis suggests a new family of synthetic carbon fixation pathways that utilize the most effective carboxylating enzyme, PEP carboxylase. I will describe how our lab approaches synthetically implementing carbon fixation within bacteria.