title: Synthesis of medium-chain fatty acids and their incorporation into triacylglycerols by cell-free fractions from Cuphea embryos.
abstract: During their rapid maturation period, seeds of Cuphea wrightii A. Gray mainly accumulate medium-chain fatty acids (C8 to C14) in their storage lipids. The rate of lipid deposition (40-50 mg·d(-1)·(g fresh weight)(-1)) is fourfold higher than in seeds of Cuphea racemosa (L. f.) Spreng, which accumulate long-chain fatty acids (C16 to C18). Measurements of the key enzymes of fatty-acid synthesis in cell-free extracts of seeds of different maturities from Cuphea wrightii show that malonyl-CoA synthesis may be a triggering factor for the observed high capacity for fatty-acid synthesis. Experiments on the incorporation of [1-(14)C]acetate into fatty acids by purified plastid preparations from embryos of Cuphea wrightii have demonstrated that the biosynthesis of medium-chain fatty acids (C8 to C14) is localized in the plastid. Thus, in the presence of cofactors for lipid synthesis (ATP, NADPH, NADH, acyl carrier protein, and sn-glycerol-3-phosphate), purified plastid fractions predominantly synthesized free fatty acids, 30% of which were of medium chain length. Transesterification of the freshly synthesized fatty acids to coenzyme A and recombination with the microsomal fraction of the embryo homogenate induced triacylglycerol synthesis. It also stimulated fatty-acid synthesis by a factor 2-3 and increased the relative amount of medium-chain fatty acids bound to triacylglycerols, which corresponded to about 60-80% in this lipid fraction.
authors.affiliation: Institut für Biochemie der Pflanze der Universität Göttingen, Untere Karspüle 2, D-3400, Göttingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Deerberg
authors.forename: J
authors.initials: J
authors.lastname: von Twickel
authors.forename: H H
authors.initials: HH
authors.lastname: Förster
authors.forename: T
authors.initials: T
authors.lastname: Cole
authors.forename: J
authors.initials: J
authors.lastname: Fuhrmann
authors.forename: K P
authors.initials: KP
authors.lastname: Heise