Synthesis of medium-chain fatty acids and their incorporation into triacylglycerols by cell-free fractions fromCupheaembryos
✍ Scribed by Silke Deerberg; Johanna Twickel; Hans-Heinrich Förster; Thomas Cole; Jochen Fuhrmann; Klaus-Peter Heise
- Publisher
- Springer-Verlag
- Year
- 1990
- Tongue
- English
- Weight
- 565 KB
- Volume
- 180
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
During their rapid maturation period, seeds of Cuphea wrightii A. Gray mainly accumulate mediumchain fatty acids (C8 to C14) in their storage lipids. The rate of lipid deposition (40-50 mg.d-l.(g fresh weight)-1) is fourfold higher than in seeds of Cuphea racemosa (L. f.) Spreng. which accumulate long-chain fatty acids (C16 to C 1 s). 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 [1-14C]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.