vernoleate and ricinoleic-acid

Oxygenated fatty acids such as ricinoleic acid and vernolic acid can serve in the industry as synthons for the synthesis of a wide range of chemicals and polymers traditionally produced by chemical conversion of petroleum derivatives. Oxygenated fatty acids can also be useful to synthesize specialty chemicals such as cosmetics and aromas. There is thus a strong interest in producing these fatty acids in seed oils (triacylglycerols) of crop species. In the last 15 years or so, much effort has been devoted to isolate key genes encoding proteins involved in the synthesis of oxygenated fatty acids and to express them in the seeds of the model plant Arabidopsis thaliana or crop species. An often overlooked but rich source of enzymes catalyzing the synthesis of oxygenated fatty acids and their esterification to glycerol is the biosynthetic pathways of the plant lipid polyesters cutin and suberin. These protective polymers found in specific tissues of all higher plants are composed of a wide variety of oxygenated fatty acids, many of which have not been reported in seed oils (e.g. saturated omega-hydroxy fatty acids and alpha,omega-diacids). The purpose of this mini-review is to give an overview of the recent advances in the biosynthesis of cutin and suberin and discuss their potential utility in producing specific oxygenated fatty acids for specialty chemicals. Special emphasis is given to the role played by specific acyltransferases and P450 fatty acid oxidases. The use of plant surfaces as possible sinks for the accumulation of high value-added lipids is also highlighted.

Topics: 1-Acylglycerol-3-Phosphate O-Acyltransferase; Arabidopsis; Arabidopsis Proteins; Cytochrome P-450 Enzyme System; Epoxy Compounds; Lipids; Membrane Lipids; Models, Biological; Oleic Acids; Plants, Genetically Modified; Ricinoleic Acids

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal beta-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward beta-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through beta-oxidation than the expression profile of genes involved in lipid metabolism.

Topics: Arabidopsis; Crepis; Epoxy Compounds; Fatty Acids; Gene Expression; Gene Expression Profiling; Genes, Plant; Genetic Engineering; Germination; Mixed Function Oxygenases; Mutation; Oleic Acids; Oxidation-Reduction; Oxidoreductases; Plant Proteins; Plants, Genetically Modified; Ricinoleic Acids; Ricinus communis; Seeds

Poly(hydroxyalkanoates) (PHAs) were isolated from Pseudomonas aeruginosa 44T1 cultivated on euphorbia oil and castor oil. With the aid of 2-D proton NMR spectra and proton-detected multiple bond coherence NMR spectra the structures of the PHAs were determined. In addition to the usual PHA constituents (C6-C14 3-hydroxy fatty acids), PHAs formed from euphorbia oil contained delta 8,9-epoxy-3-hydroxy-5c-tetradecenoate, and probably delta 6,7-epoxy-3-hydroxydodecanoate and delta 4,5-epoxy-3-hydroxydecanoate. These novel constituents account for approximately 15% of the total amount of monomers and are clearly generated via beta-oxidation of vernolic acid (delta 12,13-epoxy-9c-octadecenoic acid), the main component of euphorbia oil. In PHAs formed from castor oil, 7% of the monomers found were derived from ricinoleic acid (12-hydroxy-9c-octadecenoic acid). The presence of 3,8-dihydroxy-5c-tetradecenoate was clearly demonstrated. Furthermore, NMR analysis strongly suggested the presence of 3,6-dihydroxydodecanoate, 6-hydroxy-3c-dodecenoate, and 4-hydroxydecanoate.

Topics: Castor Oil; Epoxy Compounds; Fatty Acids; Hydroxy Acids; Magnetic Resonance Spectroscopy; Oleic Acids; Oxidation-Reduction; Plant Oils; Polyesters; Pseudomonas aeruginosa; Ricinoleic Acids