LECITHINASE SYSTEMS IN SUGAR BEET, SPINACH, CABBAGE, AND CARROT

Abstract

Lecithinase activity of aqueous extracts of sugar beet, spinach, or cabbage leaves, and of carrot root was found to be associated entirely with the plastid fractions, separated by high-speed centrifugation. The supernatant cell sap–cytoplasm fractions were not only inactive but actually inhibitory. The rate of enzymatic liberation of choline from lecithin by all plastid fractions was found to be greatly increased by saturation with diethyl ether. The influence of pH, enzyme concentration, substrate concentration, and temperature on the rate of ether-activated choline liberation was studied and optimum conditions for the reaction were determined. Under optimum conditions, liberation of choline from lecithin by each of the plastid fractions was rapid and was accompanied by a much slower liberation of inorganic and water-soluble organic phosphate; liberation of phosphates was much greater with spinach than with the other species. Thermal inactivation and fluoride inhibition of the enzyme systems were also studied.