Markov-state model for CO binding with carbonic anhydrase under confinement.

Enzyme immobilization with a nanostructure material can enhance its stability and facilitate reusability. However, the apparent activity is often compromised due to additional diffusion barriers and complex interactions with the substrates and solvent molecules. The present study elucidates the effects of the surface hydrophobicity of nano-confinement on CO diffusion to the active site of human carbonic anhydrase II (CA), an enzyme that is able to catalyze CO hydration at extremely high turnover rates. Using the Markov-state model in combination with coarse-grained molecular dynamics simulations, we demonstrate that a hydrophobic cage increases CO local density but hinders its diffusion towards the active site of CA under confinement. By contrast, a hydrophilic cage hinders CO adsorption but promotes its binding with CA. An optimal surface hydrophobicity can be identified to maximize both the CO occupation probability and the diffusion rate. The simulation results offer insight into understanding enzyme performance under nano-confinement and help us to advance broader applications of CA for CO absorption and recovery.