Kinetic behavior of soybean lipoxygenase: A comparative study of the free enzyme and the enzyme immobilized in an alginate silica sol-gel matrix

Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroper oxide into polyunsaturated fatty acids (PUFA). We recently reported a proce dure that immobilizes soybean LOX within an alginate sol-gel matrix. In thi s study, the kinetic profile of free LOX was compared with that of the sol- gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the t emperature range of 25-35C. Enzyme activity, measured in aqueous buffer, fo r both the free and immobilized LOX preparations had K-m values of 2.5 and 1.40 mmoles/L, respectively, and V-max values of 0.056 and 0.02 mu mol/min, respectively. The relative rates of oxidation of linoleic acid and acylgly cerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid > 1-monolinolein > 1,3-dilinolein > trilinolein, and for immobilized LOX was linoleic acid > 1, 3-dilinolein > 1-monolinolein > trilinolein. In general, LOX immobilized in alginate silica sol-gel matrix retained the physical and chemical characteristics of free LOX.