A method for plotting ultracentrifuge diagrams for polydisperse systems.

apparently restricted to the cotyledon as several analyses of leaf and root homogenates showed no activity. In experiments not shown here, it was found that the enzyme is present in extracts of acetone powders of eithers peanut or castor-bean cotyledons. In order to test the specificity of the malate synthetase reaction, various compounds were compared with acetyl phosphate in the assay system of Table II. With acetyl pantetheine, acetyl glutathione and fluoroacetyl phosphate 5, o.i, 0.4, and o.I /zmoles glyoxalate disappeared. The data with fluoroacetyl phosphate and acetyl pantetheine are within experimental error while the apparent activity with acetyl :glutathione may have been due to liberation of free thiol by a thiolesterase in the extract, with subsequent non-enzymic condensation with glyoxalate. To test this point, the reaction was followed by disappearance of thiol ester at 232 m/~. As shown in Fig. I neither acetyl pantetheine nor acetyl glutathione are reactive in the malate synthetase reaction and the extract does contain acetyl glutathione thiolesterase. These experiments further establish that acetylCoA is the reactive component and tha t both glyoxalate and enzyme are required for the reaction. In similar spectrophotometric experiments it was found that both propionylCoA and butyrylCoA are not active, indicating complete specificity of the reaction for acetylCoA. Two types of experiments were performed to test the reversibility of the reaction (a) incubation of malate, CoA, and enzyme with hydroxylamine and analysis for acethydroxamic acid (b) incubation of malate, CoA and enzyme with a system of removal of acetylCoA (transacetylase and arsenate) and analysis for glyoxalate. The negative results obtained in both experiments indicate that the equilibrium is far in the direction of malate and that detection of reversibility will require an extremely sensitive assay.