Fat Metabolism in Higher Plants

The discovery and isolation of the multienzyme system responsible for p oxidation of fatty acids to acetyl CoA’ have stimulated investigation of the synthesis of long chain fatty acids by multiple @ condensation of the acetyl CoA. In 1953 Van Baalen and Gurin (1) were the first to demonstrate that acetate was incorporated into fatty acids by aqueous extracts of pigeon liver. In 1953 Stansly and Beinert (2), employing the purified enzymes of the /?-oxidative system, showed the synthesis of butyryl CoA from acetyl CoA. In 1955 Hele and Popj6k (3) described soluble enzyme systems from rat and rabbit mammary glands which catalyze the synthesis of long chain fatty acids from acetate in the presence of ATP, CoA, and DPN. Langdon (4) has made the important observation that TPNH is required for the incorporation of acetate-Cl4 into the higher fatty acids by soluble liver systems. Recently Gibson and Jacob (5) and Wakil, Porter, and Tietz (6), using three different protein fractions obtained from pigeon liver and a mixture of cofactors and substrates, showed the synthesis of long chain fatty acids from acetate. In higher plants, Newcomb and Stumpf (7) observed that slices of cotyledons of both germinating and developing peanuts had the capacity to incorporate acetate-U4 into long chain fatty acids. Gibble and Kurtz (8) demonstrated that acetate-l-O4 was incorporated by developing flax fruits into long chain fatty acids which were labeled predominantly in the odd-numbered carbon atoms. Sisakyan and Smirnov (9) supplied acet,ateCl4 to sunflower chloroplasts and isolated long chain fatty acids with relatively low radioactivity. No cofactor requirements were demonstrated.