Ionic liquid activated Bacillus subtilis lipase A variants through cooperative surface substitutions

Area of Science:

• Biocatalysis and Protein Engineering
• Enzyme Activity in Non-Conventional Media
• Protein-Lipid Interactions

Background:

• Enzyme-catalyzed reactions in amphiphilic systems like ionic liquids (ILs) are gaining interest.
• Directed protein evolution is a powerful tool for tailoring enzyme properties.
• Understanding enzyme behavior in ILs is crucial for expanding biocatalysis.

Purpose of the Study:

• To identify and characterize Bacillus subtilis lipase A variants with enhanced resistance and activity in ILs.
• To investigate the mechanism of IL-activation in engineered lipase variants.
• To explore protein-IL interactions using specific lipase variants.

Main Methods:

• Directed evolution to generate lipase variants.
• Enzyme activity and resistance assays in various IL-aqueous mixtures.
• Analysis of specific activity and stability of wild-type and mutant lipases.
• Investigating the structural basis for IL-activation.

Main Results:

• Nine IL-resistant lipase A variants were identified, including an IL-activated variant M1 (M134N/N138S/L140S).
• Variant M2 (M134R/L140S) exhibited nearly doubled specific activity and resistance in 9 vol% [C4 mim][TfO].
• IL-activation of variant M1 at high IL concentrations was linked to cooperative surface substitutions and potential IL/substrate clustering.

Conclusions:

• This study presents the first example of an IL-activated lipase variant generated through protein engineering.
• The findings provide insights into protein-IL interactions and the design of enzymes for IL environments.
• Engineered lipases offer potential for biocatalysis in ionic liquid systems.