Phase-separated compartments as biochemical reactors*

Living cells use phase-separated compartments to spatially organise fuel-driven chemical reactions. Understanding how such compartments control biochemical reactions is key to elucidate the functionality of, for example stress granules for the cell. It is also crucial for the biochemical communication among synthetic cells and RNA catalysis in coacervate protocells. Not much is known about the mechanisms underlying such spatial control of chemical reactions and how much the properties of chemical reactions are altered by the compartments. Here, we derive a theoretical framework to study fuel driven chemical reactions in the presence of compartments. We study two state transitions like phosphorylation via hydrolysis of ATP and enzymatic reactions. For two state transitions, we find that the ratio of phosphorylated product can be regulated by droplets by two orders of magnitude relative to the homogenous state. In the case of enzymatic reactions, we show that the initial rate of product formation can be increased by more than ten fold. Our studies quantify the enormous potential of phase separated compartments as biochemical reactors in living cells.