INVESTIGATION OF BEHAVIOR OF AN ENZYME IN A BIPHASIC SYSTEM - SOYBEANLIPOXYGENASE-1

Soybean lipoxygenase-1 (EC 1.13.11.12) reaction with linoleic acid as substrate was used to study the biocatalysis in a biphasic system when the reactants have surface-active properties. The poorly water-solubl e substrate was initially dissolved in an apolar solvent (octane). The hydroperoxide produced was water soluble and remained in the aqueous phase (berate buffer). The bioreactor was a modified Lewis cell with a well-defined interfacial area between the two phases. Two phenomena w ere studied separately: the reactant transfer between the two phases a nd the biocatalyzed reaction in an aqueous medium. This allowed determ ination of the transfer and the reaction constants. Substrate transfer was found to be affected by the progress of the reaction, because lin oleic acid and the hydroperoxy acid have an influence on the interfaci al tension. inactivation of the biocatalyst at the interface was obser ved in the bioreactor. These results indicate that it is impossible to analyze the system behavior with the method proposed in the literatur e, which is based on the sequential study of the substrate transfer to the aqueous phase and its biocatalysis by lipoxygenase. The interacti on between transfer phenomena and reaction kinetics was studied in the biphasic system. The kinetics were different from those obtained in t he aqueous medium. Catalysis and transfer influence each other recipro cally. In this compartmentalized system, cooperativity phenomena were obtained using a nonallosteric enzyme. The evolution of the system was modeled (Runge-Kutta algorithm). The curves obtained were very close to those determined experimentally. (C) 1996 John Wiley & Sons, Inc.