Gary J. Blomquist

Biosynthesis of linoleic acid in a termite, cockroach and cricket

Abstract The de novo biosynthesis of linoleic acid was demonstrated in the cockroach, Periplaneta americana, the termite, Zootermopsis angusticollis and the cricket, Acheta domesticus. [1-14C]-acetate was incorporated into a component that co-chromatographed with a linoleate standard on silver nitrate thin layer chromatography and radio-gas-liquid chromatography. Ozonolysis of the methyl ester of the dienoic acid labelled from [1-14C]-acetate demonstrated that radioactivity was incorporated into the fragments containing carbons 1–9 and 13–18, suggesting that the entire molecule was labelled. The housefly, Musca domestica, the pea aphid, Acyrthosiphon pisum and the German cockroach, Blatella germanica, did not incorporate radioactivity from [1-14C]-acetate into linoleate.

Biosynthesis of linoleic acid in insects

Abstract The de novo biosynthesis of linoleic acid (9,12-octadecadienoic acid), generally considered an essential dietary nutrient for animals, has been demonstrated in 15 insect species representing four orders. Two of these species were also shown to further elongate and desaturate linoleic acid to form arachidonic acid, implying the ability to insert double bonds on both sides of the Δ position of oleic acid (9-octadecenoic acid).

De novo biosynthesis of linoleic acid in insects

Abstract The de novo biosynthesis of linoleic acid was demonstrated in 8 of the 32 insect species examined, which include members of three orders and encompass both holometabolous and hemimetabolous species. The incorporation of [1-14C]acetate into linoleate was demonstrated by radio-GLC, and in selected species by radio-HPLC, silver nitrate thin-layer chromatography, radio-GLC and GLC linked to mass spectrometry of ozonolysis products. In most of the species which synthesized linoleate, there was a time-dependent increase in the incorporation of [1-14C]acetate into linoleate from 2 to 24 h, and most of the labeled linoleate was recovered in the phospholipid fraction. There was no readily discernable evolutionary, physiological or nutritional pattern in the ability of certain species to synthesize linoleate.

De novo biosynthesis of polyunsaturated fatty acids in the cockroach Periplaneta americana

The de novo biosynthesis of 6,9,12-linolenic acid, 11,14-eicosadienoic acid, 5,11,14-eicosatrienoic acid, and arachidonic acid was demonstrated in adult female cockroaches, Periplaneta americana. These four polyunsaturated fatty acids (PUFA) were present primarily in the phospholipid (PL) fraction of both males and females. They were purified by AgNO3 thin-layer chromatography and high pressure liquid chromatography. The double bond positions of the major isomer of eicosatrienoic acid were shown to be at the delta 5,11,14 positions by gas chromatography-mass spectrometry (GC-MS) of both methoxy and epoxide derivatives and gas-liquid chromatography (GLC) and GC-MS of ozonolysis products. The other PUFAs cochromatographed with standards on both packed and capillary GLC columns. The in vivo incorporation of [1-14C]acetate into 5,11,14-eicosatrienoic acid, 11,14-eicosadienoic acid, 6,9,12-linolenic acid, and arachidonic acid was demonstrated by radio-GLC and radio-HPLC and for 5,11,14-eicosatrienoic acid by radio-GLC of ozonolysis products. The latter technique clearly demonstrated that the entire eicosatrienoic acid molecule was labeled. Thoracic tissue contained the highest amount of radiolabeled 5,11,14-eicosatrienoic acid (1.6% of total radioactivity incorporated into PL) while radiolabeled 11,14-eicosadienoic acid was found primarily in abdominal epidermal tissue (2% of total radioactivity incorporated into PL). Radiolabeled arachidonic and 6,9,12-linolenic acids comprised 0.1 and 0.02%, respectively, of the total radioactivity in the PL fraction. These data document the de novo biosynthesis of di-, tri-, and tetraunsaturated fatty acids in the American cockroach, and indicate that this animal can desaturate on both sides of the delta 9 double bond of oleic acid.

Biosynthesis of polyunsaturated fatty acids by the australian field cricket, Teleogryllus commodus

Abstract Aspects of testicular fatty acid biochemistry from the Australian field cricket, Teleogryllus commodus, are reported. Over 10% of the phospholipid fatty acids were C20 polyunsaturated fatty acids (PUFAs), with nearly 6% arachidonic acid (20:4). The testes and ovaries accumulated a large proportion of label from radioactive arachidonic acid that was injected into the hemocoel (about 30%). Specificity in the uptake was shown by comparison to a similar study with labelled stearic acid, in which only 1.5% of the radioactivity was taken up by testes. Sixty percent of the radioactivity taken up by testes from [3H]20:4 was incorporated into phospholipids and 30% into triacylglycerols. Fat body of males and females incorporated 27% of the [3H]20:4 into phospholipids and 68% (males) or 55% (females) into triacylglcyerols. Radioactivity from [1-14C]acetate was incorporated into testicular linoleic acid and eicosatrienoic acid, but not eicosatetraenoic acid, suggesting the de novo biosynthesis of both 18:2 and a C20 PUFA by this species. Label from injected [U-14C]linoleic acid was recovered mostly as linoleic acid, with a small portion of the recovered radioactivity in eicosatrienoic acid, but not eicosatetraenoic acid. Very little label from injected linoleic acid occurred as monounsaturated or saturated fatty acids, indicating only slight, if any, β-oxidation of 18:2 to acetate and subsequent lipid synthesis.

Site of sex pheromone biosynthesis in the female housefly,Musca domestica L.

The primary site of sex pheromone biosynthesis in the female housefly is the abdominal integument tissue, whereas the contribution of the legs is relatively minor. A substantial portion of the sex pheromone components are, however, transferred from the abdomen to the legs, probably as a result of grooming.

A 13C-NMR study of the biosynthesis of 3-methylpentacosane in the American cockroach

13C-NMR spectrometry was used to examine the in vivo incorporation of 13C-labeled precursors into 3-methylpentacosane in the cockroach Periplaneta americana. Natural abundance 13C-NMR of 3-methylpentacosane showed that carbons 1 through 6, 23 through 25 and the branching methyl carbon (C26) each gave distinct signals, with carbons 7 through 22 indistinguishable from each other. The label from dipotassium 2-[methyl-13C]methylmalonate was incorporated primarily into the methyl branch of 3-methylpentacosane, demonstrating the 2-methylmalonate is the precursor to the methyl branch unit. The carboxyl carbon from sodium [1-13C]propionate was incorporated exclusively into the 4-position. This indicates that propionate, as a 2-methylmalonyl derivative, is incorporated as the second unit during chain synthesis rather than toward the end of the elongation process. The labeled carbon from sodium [1-13C]acetate was incorporated into carbons 2, 6 and 24 and the labeled carbon from [2-13C]acetate was incorporated into carbons 1, 5, 23 and 25 of 3-methylpentacosane, respectively. These data are consistent with an elongation-decarboxylation pathway for 3-methylpentacosane biosynthesis.

De novo biosynthesis of linoleic acid in two non-insect invertebrates: The land slug and the garden snail

The de novo biosynthesis of linoleic acid [18:2(n-6)], a fatty acid considered to be essential for most animals, was demonstrated in the land snail,Bulimulis alternatus mariae, and the garden slug,Arion circumscriptus. Radiolabeled acetate injected into the animals was incorporated into both 18:2 and 20:2, as demonstrated by radio-high performance liquid chromatography (radio-HPLC) and radio-gas chromatography (radio-GC). GC-mass spectrometry (GC-MS) of the methoxy derivatives of the 18:2 and 20:2 isolated from the snail showed that major isomers had the double bonds in the n-6,9 positions. Radio-gas-liquid chromatography (radio-GLC) of the ozonolysis products from the labeled dienoic fatty acid methyl esters showed that both ends of the molecules were labeled, confirming de novo synthesis. The production of linoleic acid by these animals suggests the capability to produce linoleic acid may be widespread in invertebrates.

Insect tissues, not microorganisms, produce linoleic acid in the house cricket and the American cockroach

Biosynthesis of linoleic acid, 18∶2(n−6), was unambiguously demonstrated to occur in the cockroach,Periplaneta americana, and the cricket,Acheta domesticus. Axenic tissue from both of these insect species was demonstrated by radio-gas-liquid chromatography (radio-GLC) and radio-high-performance liquid chromatography (radio-HPLC) to incorporate [1-14C]acetate and [1-14C]oleate into this essential fatty acid.