The hydration layer of the enzyme in the bulk gas phase has great effects on its catalytic performance. Molecular dynamics (MD) simulations at all-atom level was applied to investigate the effects of the hydration layer thickness on the diffusion of carbon dioxide molecules into the active site of a carbonic anhydrase enzyme from a bulk gas phase. Based on the distribution of water molecules surrounding the carbonic anhydrase enzyme

the effects of the hydration layer thickness on the protein structure and CO2 transport from the bulk gas phase to the protein active site was studied. The simulation results suggested an optimal hydration layer thickness of 0.7 nm for CO2 diffusion. The CO2 adsorption sites were identified

which compose of the diffusion channel inside the carbonic anhydrase. The MD simulation revealed the open states of these adsorption sites

which may be useful to identify the bottleneck position of the diffusion channel. The molecular insight is helpful for design and optimization of carbonic anhydrase

enabling more efficient CO2 adsorption and conversion.