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Enzymatic catalysis in nonaqueous solvents.
1Department of Applied Biological Sciences, Massachusetts Institute of Technology, Cambridge 02139.
The Journal of Biological Chemistry
|March 5, 1988
Summary
Enzymes like subtilisin and alpha-chymotrypsin catalyze reactions in organic solvents, with activity linked to solvent hydrophobicity. Essential water and solvent interactions significantly impact enzyme function and stability in non-aqueous media.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Organic chemistry
Background:
- Subtilisin and alpha-chymotrypsin are proteases known for their catalytic activity.
- Enzymatic catalysis typically occurs in aqueous environments.
- Organic solvents offer unique reaction media with potential benefits for enzyme stability and activity.
Purpose of the Study:
- To investigate the catalytic activity and kinetics of subtilisin and alpha-chymotrypsin in various dry organic solvents.
- To explore the role of water and solvent properties in enzyme performance in non-aqueous media.
- To assess the impact of organic solvents on enzyme stability and specificity.
Main Methods:
- Enzymatic transesterification reactions were performed in different organic solvents.
- Michaelis-Menten kinetics were analyzed to determine kinetic parameters (V/Km).
- Enzyme stability was evaluated under various storage and thermal conditions in both aqueous and non-aqueous solvents.
- Competitive inhibition studies were conducted to assess enzyme specificity.
Main Results:
- Enzymes exhibited vigorous catalytic activity in dry organic solvents, with activity correlating to solvent hydrophobicity.
- Minimal water, less than a monolayer, was sufficient for catalysis.
- Hydrophilic solvents reduced enzyme activity by stripping essential water and directly affecting the enzyme.
- Rate enhancements of 100 billion-fold were observed in octane.
- Enzyme specificity reversed in octane compared to water.
- Significantly enhanced thermal and storage stability in non-aqueous solvents.
Conclusions:
- Enzymatic catalysis is feasible and highly efficient in dry organic solvents.
- Solvent properties, particularly hydrophobicity and water content, critically influence enzyme activity and stability.
- The structural rigidity of enzymes in organic solvents contributes to enhanced stability and altered catalytic behavior.
- Organic solvents represent a promising medium for enzyme applications, offering improved stability and tunable specificity.