Marcus, L., Department of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Prusky, D., Department of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Jacoby, B., Department of Fruit and Vegetable Storage, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel, Department of Agricultural Botany, Faculty of Agriculture, Hebrew University of Jerusalem, P.O.B. 12, Rehovot, 76100, Israel

Lipoxygenase (E.C.1.13.1.13) from the avocado cultivar 'Fuerte' was purified to near homogeniety by affinity chromatography. The enzyme was extracted in potassium phosphate buffer at pH 7.2 in the presence of 2% Triton X-100. Triton was removed from the homogenate by adsorption on 250-350 mesh activated charcoal. Lipoxygenase was partially purified (seven-fold) by 66% acetone precipitation from a 20% acetone supernatant. The precipitate was dissolved in a potassium phosphate buffer at pH 7.2 and loaded on an affinity chromatography column. This single-step chromatographic purification yielded a single lipoxygenase activity peak. The total activity yield of the purification procedure was ca 65% and the degree of enrichment ca 35-fold. The Mr determined by gel filtration and by electrophoresis, was 74 000. Optimum enzyme activity was found at 36° and pH 7.1. The energy of activation, amino acid composition, isoelectric point, kinetic parameters and inhibitory effect of epicatechin were studied. The enzyme was found to obey Michaelis-Menten kinetics. The Km of the avocado lipoxygenase for linoleate was 7.2 × 10-2 mM and the Vmax, was 432 μmol/hr/mg. Epicatechin acted as a competitive inhibitor with a Ki of 9.0 × 10-5 mM. © 1988.