Cysteine protease inhibition by nitrile-based inhibitors: a computational study

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzyme Inhibition

Background:

• Cysteine proteases are crucial for human physiology, mediating protein degradation via a cysteine-histidine catalytic mechanism.
• Nitrile-based compounds are potent inhibitors, but their precise reaction mechanisms remain unclear.
• Understanding these mechanisms is vital for designing effective therapeutic agents.

Purpose of the Study:

• To elucidate the reaction mechanism of nitrile-based inhibitors with cysteine protease active sites.
• To investigate the impact of structural modifications on inhibitor efficiency.
• To compare computational modeling approaches for studying these enzymatic reactions.

Main Methods:

• Combined density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) computational study.
• Analysis of nitrile-based inhibitor reactions with enzyme active site amino acids.
• Investigation of mechanical vs. electronic embedding in QM/MM.

Main Results:

• Minor structural changes in inhibitors drastically alter catalysis and inhibition, reducing efficiency by orders of magnitude.
• DFT calculations showed significant structural distortions, unsuitable for the enzyme active site.
• QM/MM with electronic embedding revealed substantial differences in geometry and thermodynamics compared to mechanical embedding.

Conclusions:

• The choice of computational model significantly influences the accuracy of studying cysteine protease inhibition.
• Accurate modeling is essential for understanding structure-activity relationships and designing effective enzyme inhibitors.
• Electronic embedding in QM/MM is critical for capturing accurate reaction energetics and geometries.