Biosynthesis of Fatty Acids by a Soluble Extract from Developing Soybean Cotyledons

Fractionation of developing soybean cotyledons into cellular components demonstrates that most of the activity necessary to incorporate acetate-1-(14)C into lipid remains in the supernatant from a 198,000g spin for 1 hr. The system studied is dependent upon ATP, CoA, and CO(2). Concentrations of ATP greater than 4 x 10(-3)m are inhibitory, while 1 x 10(-4)m CoA is needed for optimal activity. Avidin inhibition of acetate incorporation into lipid could be reversed by biotin. Studies indicated that NADPH is a better source of reducing power than NADH. The system studied is inhibited by p-chloromercuribenzoic acid and this inhibition can be reversed by an excess of GSH. The system studied shows maximum activity in tris buffer at pH 8.6 or in glycine buffer, pH 9.4.The distribution of acetate into the various fatty acids is greatly influenced by the temperature of incubation. Cooler incubation temperatures favor the distribution of acetate into the more unsaturated fatty acids.