Studying O₂ pathways in [NiFe]- and [NiFeSe]-hydrogenases

Prior research has shown that [NiFe]-hydrogenases are highly active in hydrogen oxidation but are sensitive to oxygen. It was already known that [NiFeSe]-hydrogenases exhibit greater tolerance to aerobic conditions. However, the structural basis for this difference remained unclear. No prior work had resolved how oxygen permeation pathways differ between these enzyme types. This gap motivated the current investigation into the molecular mechanisms behind oxygen resistance. Understanding these differences could improve the design of hydrogenases for biotechnological use. The role of selenium in modulating oxygen sensitivity was not fully understood. This study builds on existing knowledge of hydrogenase structure and function.

The aim of this study was to investigate the structural reasons behind the reduced oxygen sensitivity in [NiFeSe]-hydrogenases. The specific problem addressed was the lack of detailed understanding of oxygen permeation pathways in these enzymes. The motivation came from the potential to enhance hydrogenase stability in oxygen-rich environments. By comparing [NiFe] and [NiFeSe] hydrogenases, the researchers sought to identify key differences in oxygen diffusion. The goal was to map oxygen pathways and assess their energetic feasibility. This would help explain the observed experimental differences in oxygen inhibition. The study focused on computational methods to model and compare enzyme behavior. The findings could inform future enzyme engineering efforts.

The researchers employed computational methods to model oxygen diffusion in hydrogenases. Molecular Dynamics simulations were used with explicit oxygen molecules. Implicit Ligand Sampling was applied to map free energy landscapes for oxygen permeation. These simulations allowed the identification of oxygen pathways in both enzyme types. Reactive flux analysis was performed to determine the most relevant pathways. Transition path theory was used to assess the kinetic relevance of these pathways. The study compared the structural features of [NiFe] and [NiFeSe] hydrogenases. Residue positions lining oxygen pathways were identified and analyzed. The methods combined simulation and theoretical analysis to evaluate oxygen permeation efficiency.

The study found that [NiFeSe]-hydrogenases have distinct oxygen pathways compared to [NiFe] enzymes. Free energy landscapes revealed lower permeation efficiency in [NiFeSe]-hydrogenases. Oxygen diffusion was predicted to be less effective in the [NiFeSe] enzyme. The most relevant pathways were identified through reactive flux analysis. These pathways differ significantly between the two enzyme classes. Residue positions lining the oxygen pathways were mapped in both enzymes. The results suggest that structural differences reduce oxygen access to the active site. These findings align with experimental observations of reduced oxygen inhibition in [NiFeSe]-hydrogenases.

The authors suggest that structural differences in [NiFeSe]-hydrogenases contribute to their lower oxygen sensitivity. The study supports the idea that oxygen permeation pathways are less efficient in [NiFeSe] enzymes. These findings may help explain the observed experimental tolerance to oxygen. The results are consistent with prior observations of [NiFeSe] hydrogenase stability. The study does not propose new applications but highlights structural insights. The authors do not claim essentiality of any specific residue or pathway. The conclusions are based on computational evidence from simulations and energy mapping. The work provides a foundation for future studies on hydrogenase oxygen resistance.