Engineering the Composition of Heterogeneous Lipid Bilayers to Stabilize Tethered Enzymes

As surfaces for enzyme immobilization, lipid bilayers (LBs) have the potential to exhibit chaperone‐like activity, which can greatly enhance enzyme stability. Here, it is shown that this stabilizing effect can be generalized to a broad range of enzymes by modifying the mixed lipid composition based on the properties of the enzyme. This is demonstrated by analyzing the stability of nitroreductase, lipase, organophosphorus hydrolase, and lysozyme on LBs composed by mixing zwitterionic 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine with anionic 1,2‐dioleoyl‐sn‐glycero‐3‐phospho‐(1′‐rac‐glycerol) or cationic 1,2‐dioleoyl‐sn‐glycero‐3‐ethylphosphocholine. Interestingly, while the optimal lipid composition exhibits a zeta potential with the same sign as each enzyme, the stabilizing compositional ranges are broad, and mixed lipid LBs are more stabilizing than homogeneous LBs with similar charge. This suggests that net charge and compositional heterogeneity are both important factors. Moreover, the degree of stabilization on appropriate bilayers under extremely denaturing conditions (7 m urea) is unprecedented, and activity of the enzymes is up to three‐fold greater than that of the soluble enzyme at each enzyme's temperature optimum. By correlating enzyme diffusion on LBs with information about re‐folding kinetics derived from single‐molecule measurements, the influence of charge and composition on enzyme‐LB interactions is shown, providing a rationale for the stabilizing effect of heterogeneous LBs. Heterogeneous lipid bilayers offer immense potential as materials for stabilizing a broad range of immobilized enzymes. This stabilizing effect can be explained by the impact of bilayer composition and charge on the strength of LB‐enzyme interactions. These findings provide insight into the role of lipid mixtures as well as surface heterogeneity and charge on enzyme stability in near‐surface environments.