The Incorporation of Glycolytic Intermediates into Lipids by Plastids Isolated from the Developing Endosperm of Castor Oil Seeds (Ricinus communisL.)

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Abstract
Plastids were isolated from the developing endosperm of Ricinus communis L. and purified by rate-zonal centrifugation on discontinuous sucrose gradients. Assay conditions were optimized for the uptake and incorporation of 14C-acetate into lipids by intact plastids. Using the optimized conditions, the uptake and incorporation of several 14C-glycolytic intermediates into lipids were examined. Neither sucrose nor glucose-6-phosphate was incorporated into lipids. In order of increasing magnitude of incorporation, glucose, fructose, 3-phosphoglycerate, acetate, and pyruvate were metabolized to chloroform-methanol (2: 1 v/v) soluble products. Pyridoxal-5'-phosphate inhibited the incorporation of 3-phosphoglycerate into lipids whereas α-cyano-4 hydroxycinnamate was without effect on pyruvate incorporation. Avidin and cerulenin did not inhibit the incorporation of acetate into lipids by intact plastids.