Single-Entity Protein Electrochemistry of Diffusion-Limited Enzymes

In this work, we present single-entity protein electrochemistry (SEPE) experiments on catalase, along with a theoretical model to simulate its enzymatic activity and predict the experimentally observed current responses. We perform SEPE measurements at various enzyme concentrations and use protein film voltammetry to investigate the origin of the observed electrochemical signals in SEPE. The modeling approach we develop combines finite element simulations in COMSOL Multiphysics with random walk simulations in MATLAB. The enzyme is represented as a partially active sphere, with an arc on the surface corresponding to the enzyme’s diffusion channel leading to the active site. Notably, the model reproduces the experimental data for catalase without invoking fluctuations in enzymatic activity. This modeling approach, which accounts for the active site geometry of the enzyme, can be useful for simulating single-entity protein electrochemistry data for other enzymes.