Enhanced Diffusion of Single, Lipid-Tethered Enzymes.

Recent experimental evidence has shown that enzymes that catalyze exergonic reactions are able to diffuse faster during catalysis, a process called "enhanced diffusion". If true, enzyme propulsion could enable the engineering of designed active materials at the nanoscale. However, further experimental validation is needed under well-controlled conditions. We use single-molecule tracking of enzymes tethered to fluid lipid bilayers, which serve to constrain motion to two dimensions, lower baseline diffusion for improved sensitivity, and accommodate multiple tethering strategies. We find that active urease diffuses approximately 40% faster in the presence of substrate (urea) than in its absence or when inhibited, independent of the tethering scheme. The degree of enhancement scales with the substrate concentration, consistent with prior studies. Finally, we find that assembling multiple enzymes into larger complexes results in even greater diffusion enhancement. This work indicates that enzymes could serve as a platform to create and study active particles at the nanoscale.