Schaffer, A.A., Department of Horticulture, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel

The sucrose catabolic enzymes acid invertase (EC 3.2.1.26) and alkaline invertase (EC 3.2.1.27) were studied in young and mature Citrus sinensis leaf tissue. In young, expanding leaves (60 % final length) soluble acid invertase activity predominated, while soluble alkaline invertase activity predominated in mature leaves. The acid and alkaline invertase activities were separated on Sephadex G-200. The acid invertase had an Mr of approximately 60 000, pH maximum of 4.5 and apparent Km of 3.3 mM sucrose. The alkaline invertase had an Mr of approximately 200 000, pH maxima of 6.8 and an apparent Km of 20 mM sucrose. Alkaline invertase was strongly inhibited by 10 mM Tris while acid invertase was not. Possible physiological roles for the two invertases are discussed. © 1986.