  Phase-separated liquid condensates can spatially organize and thereby
regulate chemical processes. However, the physicochemical mechanisms underlying
such regulation remain elusive as the intramolecular interactions responsible
for phase separation give rise to a coupling between diffusion and chemical
reactions at non-dilute conditions. Here, we derive a theoretical framework
that decouples the phase separation of scaffold molecules from the reaction
kinetics of diluted clients. As a result, phase volume and client partitioning
coefficients become control parameters, which enables us to dissect the impact
of phase-separated condensates on chemical reactions. We apply this framework
to two chemical processes and show how condensates affect the yield of
reversible chemical reactions and the initial rate of a simple assembly
process. In both cases, we find an optimal condensate volume at which the
respective chemical reaction property is maximal. Our work can be applied to
experimentally quantify how condensed phases alter chemical processes in
systems biology and unravel the mechanisms of how biomolecular condensates
regulate biochemistry in living cells.
