Comparison of three ionic liquid-tolerant cellulases by molecular dynamics

Area of Science:

• Biochemistry
• Computational Biology
• Enzyme Engineering

Background:

• Ionic liquids (ILs) are promising solvents for biomass processing but can affect enzyme stability.
• Understanding cellulase tolerance to ILs is crucial for optimizing enzymatic biofuel production.

Purpose of the Study:

• To investigate the molecular mechanisms underlying differential ionic liquid tolerance in three family 5 cellulases.
• To correlate enzyme surface charge with stability in ionic liquid-water mixtures.

Main Methods:

• Molecular dynamics (MD) simulations were performed on cellulases from Trichoderma viride, Thermogata maritima, and Pyrococcus horikoshii.
• Simulations were conducted across a range of temperatures in binary mixtures of 1-ethyl-3-methyl-imidazolium acetate and water.

Main Results:

• Ionic liquids induced varied structural changes, from local disturbances to secondary structure loss.
• Cellulases with more negatively charged surfaces exhibited greater resistance to IL-induced destabilization.
• Less tolerant enzymes showed secondary structure disruption, altered dynamics, and binding pocket changes; one enzyme denatured within 500 ns.

Conclusions:

• Molecular dynamics provides atomic-level insights into enzyme behavior in ILs, surpassing macroscopic prediction methods.
• Specific structural and dynamic changes induced by ILs were identified for each cellulase.
• Experimentally testable hypotheses were proposed to explain IL-induced activity loss in the studied cellulases.