Distribution and Properties of Isocitritase in Plants.

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Abstract
Twenty-five plant tissues were examined for isocitritase activity. The enzyme was found to be confined to fatty tissues, particularly those of germinating seedlings rich in fat, such as sunflower, soybean, peanut, watermelon and castor bean. It was sharply localized in these tissues to those parts in which the fat is being broken down; it is not present in the ripe seed or in the seedling after the fat has been utilized. This evidence suggests that the enzyme is intimately involved in fat utilization in such seedlings. The isocitritase from castor beans has been purified some 30 fold. Like its counterpart from microorganisms the enzyme requires a sulfhydryl compound and Mg++ for optimal activity. The Km was found to be 3.2 x 10-4 [image]. The reverse reaction, i.e. formation of isocitrate from glyoxylate and succinate was demonstrated also.