Isocitrate lyase in germinating Soybean

In plant seeds, the action of the glyoxylate cycle is essential to the net synthesis of carbohydrates from reserve lipids. Isocitrate lyase (EC 4.1.3.1), which catalyses the cleavage of isocitrate into succinate and glyoxylate, is specific to this cycle. Its in vivo activity may be used as a direct measurement of the occurrence of this peculiar metabolic pathway. Using germinating soybean (Glycine max., var. Maple arrow), we present the evolution of isocitrate activity, which is best explainded by induction phenomena. Also, the enzyme from 5-day germinated cotyledons war purified using conventional techniques and various physico-chemical and reactional were determined. Its relative molecular mass is ca. 100 000, and the Km for isocitrate is equal to 1.75 mM