Application of active-phase plot to the kinetic analysis of lipoxygenase in reverse micelles

A new plot for explaining the complex expression of the enzymic activity in reverse micelles has been developed as an extension of the theoretical model described by our group [Bru, Sánchez-Ferrer & García-Carmona (1990) Biochem. J. 268, 679-684]. The plot describes the changes in the relative volume, amount of enzyme (mumoles), enzyme concentration (microM) and substrate concentration (microM) in the phase where the enzyme is active. To illustrate the usefulness of this plot, the complex activity of soya bean lipoxygenase in reverse micelles acting on its interfacial substrate, octadecadienoic acid, was studied. It showed the key parameters ruling the activity profiles of lipoxygenase with respect to micelle size (omega 0), micelle concentration (theta) and the substrate/surfactant molar ratio (rho), which have never been described before.