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Effect of nonionic detergents on lipoxygenase catalysis
M J Schilstra1, G A Veldink, J F Vliegenthart
1Bijvoet Center for Biomolecular Research, Department of Bio-Organic Chemistry, Utrecht University, The Netherlands.
Lipids
|April 1, 1994
Summary
Nonionic detergents affect soybean lipoxygenase kinetics by altering linoleate concentration. Monomeric linoleate is the preferred substrate, with detergents influencing reaction rates through micelle formation.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Lipoxygenase catalysis
Background:
- Nonionic detergents are commonly used in lipoxygenase studies to solubilize fatty acid substrates.
- Controversies exist regarding the interpretation of kinetic data in the presence of these detergents.
Purpose of the Study:
- To systematically investigate the effects of Lubrol, Tween-20, and Triton X-100 on soybean lipoxygenase kinetics.
- To resolve ambiguities in interpreting kinetic data influenced by nonionic detergents.
Main Methods:
- Studied the dioxygenation kinetics of linoleate catalyzed by lipoxygenase-1 and lipoxygenase-2.
- Varied detergent concentrations (0-0.8 g/L) and linoleate concentrations (2.5-110 microM) at pH 9-10 and 25°C.
- Developed and applied a kinetic model incorporating detergent micelle formation and substrate partitioning.
Main Results:
- Detergents generally slowed lipoxygenase-catalyzed dioxygenation.
- At high linoleate concentrations, low detergent levels increased the reaction rate due to substrate inhibition.
- A kinetic model accurately predicted experimental results by considering linoleate incorporation into detergent micelles.
Conclusions:
- Monomeric, non-micellar linoleate is the preferred substrate for soybean lipoxygenase.
- Observed inhibition and stimulation effects are attributed to changes in the effective linoleate concentration.
- The findings corroborate previous observations on detergent-influenced lipoxygenase activity.