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Defining Substrate Specificities for Lipase and Phospholipase Candidates
Published on: November 23, 2016
Water activity and substrate concentration effects on lipase activity.
1Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, S-221 00 Lund, Sweden. ernst.wehtje@biotek.lu.se
Biotechnology and Bioengineering
|July 19, 2008
Summary
Water activity significantly impacts lipase enzyme kinetics in organic solvents. Enzyme activity generally increases with water, but substrate affinity (Km) changes due to water competition and enzyme saturation.
Area of Science:
- Biocatalysis
- Enzyme kinetics
- Organic media
Background:
- Lipases are versatile enzymes used in organic synthesis.
- Water activity is a critical factor influencing enzyme performance in non-aqueous systems.
- Understanding these effects is crucial for optimizing biocatalytic processes.
Purpose of the Study:
- To investigate the effect of water activity on the catalytic activity of lipases from Rhizopus arrhizus, Candida rugosa, and Pseudomonas sp. in organic media.
- To elucidate the kinetic mechanisms underlying these water-dependent changes.
- To assess the influence of solvent properties on lipase performance.
Main Methods:
- Enzyme kinetic studies (Vmax, Km) were performed using esterification and hydrolysis reactions.
- Reactions were conducted in organic solvents, primarily diisopropyl ether.
- Water activity was systematically varied to observe its effects.
Main Results:
- Enzyme activity (Vmax) generally increased with rising water activity for all three lipases.
- In esterification, Km for alcohol increased significantly with water activity, attributed to water acting as a competing nucleophile.
- In hydrolysis, apparent Km for ester increased with water activity due to enzyme saturation by water.
Conclusions:
- Water activity plays a complex role in lipase-catalyzed reactions, affecting both maximum velocity and substrate affinity.
- The observed kinetic changes are mechanistically explained by competitive inhibition and enzyme saturation effects.
- Solvent hydrophobicity influences apparent Km for alcohol substrates, suggesting solvent choice is important for optimizing lipase performance.
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