Citrate Cleavage Enzymes from Developing Soybean Cotyledons

Data are presented which demonstrate a citrate cleavage enzyme in the supernatant of a developing soybean (Glycine max L. Merr., var. Harosoy 63) cotyledon homogenate following a 126,000g spin for 2 hours. Activity of the enzyme was observed directly in the supernatant enzyme preparation and in a desalted supernatant preparation by measuring the formation of acetylhydroxamate. Acetylhydroxamate production was dependent on citrate and coenzyme A. The reaction increased with time, citrate, and coenzyme A concentrations.Involvement of the enzyme in lipid synthesis was investigated by the incorporation of carbon from citrate-1,5-(14)C into fatty acids. Incorporation shows a pH optimum at 8.5, a temperature optimum at 30 C, and a dependence on ATP and coenzyme A. The reaction is linear throughout the range of extract concentrations tested and is linear as a function of time for 1 hour. Isotope was distributed primarily in unsaturated fatty acids.