Stereospecificity of the (Z)-9 desaturase that converts (E)-11-tetradecenoic acid into (Z,E)-9,11-tetradecadienoic acid in the biosynthesis of Spodoptera littoralis sex pheromone

A Comprehensive Review of Chemistry, Sources and Bioavailability of Omega-3 Fatty Acids

Omega-3 fatty acids, one of the key building blocks of cell membranes, have been of particular interest to scientists for many years. However, only a small group of the most important omega-3 polyunsaturated fatty acids are considered. This full-length review presents a broad and relatively complete cross-section of knowledge about omega-3 monounsaturated fatty acids, polyunsaturates, and an outline of their modifications. This is important because all these subgroups undoubtedly play an important role in the function of organisms. Some monounsaturated omega-3s are pheromone precursors in insects. Polyunsaturates with a very long chain are commonly found in the central nervous system and mammalian testes, in sponge organisms, and are also immunomodulating agents. Numerous modifications of omega-3 acids are plant hormones. Their chemical structure, chemical binding (in triacylglycerols, phospholipids, and ethyl esters) and bioavailability have been widely discussed indicating a correlation between the last two. Particular attention is paid to the effective methods of supplementation, and a detailed list of sources of omega-3 acids is presented, with meticulous reference to the generally available food. Both the oral and parenteral routes of administration are taken into account, and the omega-3 transport through the blood-brain barrier is mentioned. Having different eating habits in mind, the interactions between food fatty acids intake are discussed. Omega-3 acids are very susceptible to oxidation, and storage conditions often lead to a dramatic increase in this exposure. Therefore, the effect of oxidation on their bioavailability is briefly outlined.

From the configurational preference of dihydroceramide desaturase-1 towards Δ6-unsaturated substrates to the discovery of a new inhibitor

Dihydroceramide desaturase 1 (Des1) catalyzes the last step of ceramide synthesis de novo, thus regulating the physiologically relevant balance between dihydrosphingolipids and sphingolipids. Here we report on the configurational preference of Des1 towards isomeric Δ⁶-unsaturated dihydroceramide analogs and the discovery of a potent Des1 inhibitor.

Applications of stereospecifically-labeled Fatty acids in oxygenase and desaturase biochemistry

Oxygenation and desaturation reactions are inherently associated with the abstraction of a hydrogen from the fatty acid substrate. Since the first published application in 1965, stereospecific placement of a labeled hydrogen isotope (deuterium or tritium) at the reacting carbons has proven a highly effective strategy for investigating the chemical mechanisms catalyzed by lipoxygenases, hemoprotein fatty acid dioxygenases including cyclooxygenases, cytochromes P450, and also the desaturases and isomerases. This review presents a synopsis of all published studies through 2010 on the synthesis and use of stereospecifically labeled fatty acids (71 references), and highlights some of the mechanistic insights gained by application of stereospecifically labeled fatty acids.

Pheromone biosynthetic pathways: PBAN-regulated rate-limiting steps and differential expression of desaturase genes in moth species

We combine the use of labeled precursors with enzyme inhibitors to decipher the biosynthetic pathway of pheromone biosynthesis and the rate-limiting step/s that are regulated by pheromone biosynthesis activating neuropeptide (PBAN). We demonstrate that Plodia interpunctella is able to utilize hexadecanoic acid, and to a lesser extent tetradecanoic acid, for the biosynthesis of the main pheromone component (Z,E)-9,12-tetradecadienyl acetate. This indicated that the main pathway involves a Delta11 desaturase, chain shortening, followed by a Delta12 desaturase, but that a functional Delta9 desaturase could also be utilized. Using reverse transcription-quantitative real-time polymerase chain reaction (RT-QPCR) we distinguish two out of nine possible desaturase gene transcripts in P. interpunctella that are expressed at the highest levels. The rate-limiting step for PBAN-stimulation was studied in two moth species so as to compare the biosynthesis of a diene (P. interpunctella) and a monoene (Helicoverpa armigera) main pheromone component. In both species, incorporation of label from the (13)C sodium acetate precursor was activated by PBAN whereas no stimulatory action was observed in the incorporation of the precursors: (13)C malonyl coenzyme A; hexadecanoic 16,16,16-(2)H(3) or tetradecanoic 14,14,14-(2)H(3) acids. The acetyl coenzyme A carboxylase (ACCase) inhibitor, Tralkoxydim, inhibited the PBAN-stimulation of incorporation of stable isotope whereas the fatty-acyl reductase inhibitor, Mevastatin, failed to influence the stimulatory action of PBAN. These results provide irrefutable support to the hypothesis that PBAN affects the production of malonyl coenzyme A from acetate by the action of ACCase in the pheromone glands of these moths.

Functional characterization of a desaturase from the tobacco hornworm moth (Manduca sexta) with bifunctional Z11- and 10,12-desaturase activity

The pheromone blend produced by the tobacco hornworm moth (Manduca sexta) (L.) female is unusually complex and contains two conjugated dienals and trienals together with two monounsaturated alkenals. Here, we describe the identification and construction of two genes encoding MsexKPSE and MsexAPTQ desaturases from a cDNA library prepared from the total RNA of the M. sexta pheromone gland. The MsexKPSE desaturase shares a high degree of similarity with Delta(9)-desaturases from different moth species. The functional expression of MsexAPTQ desaturase in Saccharomyces cerevisiae followed by a detailed GC-MS analysis of fatty acid methyl esters (FAME) and their derivatized products and gas-phase Fourier transform infrared (FTIR) spectroscopy of the extracted FAME confirms that this enzyme is a bifunctional Z-Delta(11)-desaturase. MsexAPTQ desaturase catalyses the production of Z11-hexadecenoate (Z11-16) and Z10E12- and E10E12-hexadecadienoates (Z10E12-16) via 1,4-desaturation of the Z11-16 substrate. The stereochemistry of 1,4-desaturation and formation of isomers is discussed.

Expression and evolution of delta9 and delta11 desaturase genes in the moth Spodoptera littoralis

Desaturation of fatty acids is a key reaction in the biosynthesis of moth sex pheromones. The main component of Spodoptera littoralis sex pheromone blend is produced by the action of Delta11 and Delta9 desaturases. In this article, we report on the cloning of four desaturase-like genes in this species: one from the fat body (Sls-FL1) and three (Sls-FL2, Sls-FL3 and Sls-FL4) from the pheromone gland. By means of a computational/phylogenetic method, as well as functional assays, the desaturase gene products have been characterized. The fat body gene expressed a Delta9 desaturase that produced (Z)-9-hexadecenoic and (Z)-9-octadecenoic acids in a (1:4.5) ratio, whereas the pheromone gland Sls-FL2 expressed a Delta9 desaturase that produced (Z)-9-hexadecenoic and (Z)-9-octadecenoic acids in a (1.5:1) ratio. Although both Delta9 desaturases produced (Z)-9-tetradecenoic acid from myristic acid, transformed yeast grown in the presence of a mixture of myristic and (E)-11-tetradecenoic acids produced (Z,E)-9,11-tetradecadienoic acid, but not (Z)-9-tetradecenoic acid. The Sls-FL3 gene expressed a protein that produced a mixture of (E)-11-tetradecenoic, (Z)-11-tetradecenoic, (Z)-11-hexadecenoic and (Z)-11-octadecenoic acids in a 5:4:60:31 ratio. Despite having all the characteristics of a desaturase gene, no function could be found for Sls-FL4.

Synthesis of fluorinated analogs of myristic acid as potential inhibitors of egyptian armyworm (Spodoptera littorialis) Δ11 desaturasedesaturase

To study the activity of the different desaturases present in the pheromone biosynthetic pathway of the Egyptian armyworm, Spodoptera littoralis, we prepared a series of mono- and gem-difluorinated analogs of myristic acid with halogen substitution at the C8-C11 positions of the aliphatic chain via specifically positioned dithiane precursors. Thus, transformation of dithianes by treatment with N-bromosuccinimide in the presence of H2O followed by reduction with LiAlH4 afforded the appropriate alcohols, which reacted with diethylaminosulfur trifluoride to give rise to the corresponding monofluoroderivative intermediates. Alternatively, the introduction of the gem-difluoro functionality was carried out by reaction of the appropriate dithiane intermediate with 1,3-dibromo-5,5-dimethylhydantoin in the presence of HF/pyridine. The activity of these fluorinated FA as substrates and inhibitors of the desaturases involved in the biosynthesis of the sex pheromonal blend of S. littoralis has been studied. In this case, 11-fluorotetradecanoic acid elicited a moderate inhibitory activity of delta11 desaturase.