Enzymes of the Glyoxylate Cycle in Germinating

of conversion of fat to carbohydrate in germinating castor beans. Of the four requisite enzymes, isocitritase (Equation 3) has been demonstrated by direct assay (l), while the presence of condensing enzyme (Equation 1), aconitase (Equation 2), and malate synthetase activity (Equation 4) has been inferred from isotope incorporation data. The rates of condensing enzyme and malate synthetase, as estimated from the isotope data, were considerably lower than the rate of fat conversion by the intact seed. More recently, a study with germinating peanut and sunflower seeds (3) yielded results similar to those obtained earlier with castor beans. In a previous communication from this laboratory (4), direct evidence was presented for the malate synthetase reaction in germinating peanuts, and a distribution study indicated that this reaction was associated primarily with high fat seeds. The present report is concerned with the rates of reaction of the various enzymes, their cellular localization, and the relationship to the germination process. Data on TPN-isocitric dehydrogenase are also presented because of its relevance to competition for isocitrate by the glyoxylate and tricarboxylic acid cycles.