Enhancement of Enzymatic Activity by Biomolecular Condensates through pH Buffering

Biomolecular condensates can affect enzymatic reactions by locally changing not only concentrations of molecules but also their environment. Since protein conformations can differ between the dense and dilute phase, phase separation can particularly modulate enzymes characterized by a conformation-dependent activity. Here, we generate enzymatic condensates based on a lipase from Bacillus thermocatenulatus, which exhibits an equilibrium between a closed, inactive state, and an open, active conformation. We show that the activity of the enzyme increases inside the dense phase, leading to an enhancement of the overall reaction rate in the phase-separated system. Moreover, we demonstrate that these condensates can generate a more basic environment compared to the surrounding solution. As a consequence, the phase-separated system maintains a high enzymatic activity even in acidic conditions that would be otherwise less favourable for the lipase. We further show that the formation of two phases with distinct pH values optimizes a cascade reaction involving two enzymes with different optimal pH conditions. Our results demonstrate that biomolecular condensates can also affect the dependence of enzymatic rates on solution pH, thereby expanding the accessible pH interval and enabling network reactions with enzymes that require distinct pH values. These findings have crucial implications in biology and biotechnology for biocatalytic engineering.