Cuticular lipids of insects: V. Cuticular wax esters of secondary alcohols from the grasshoppersMelanoplus packardii andMelanoplus sanguinipes

Wax esters of secondary alcohols constitute 18–20% of the cuticular lipid extract ofMelanoplus packardii and 26–31% of the cuticular lipids ofMelanoplus sanguinipes. The total number of carbons in the wax esters range from 37–54 with 41 predominating in both species. The fatty acids ofM. packardii wax esters are 16∶0, 18∶0, 14∶0, 20∶0 and 12∶0 in decreasing quantity. The fatty acids ofM. sanguinipes wax esters are 18∶0, 20∶0, 16∶0 22∶0, 14∶0, 19∶0 and 17∶0 in decreasing quantity. The secondary alcohols from the wax esters ofM. packardii are C₂₅, C₂₃ and C₂₇ in decreasing quantity, and the secondary alcohols of theM. sanguinipes are C₂₃, C₂₅, C₂₁, C₂₇, C₂₄, C₂₂ and C₂₆ in decreasing quantity. Each secondary alcohol consists of two to four isomers with the hydroxyl group located near the center of the chain. Montana Agriculture Experiment Station, Journal Series No. 332.     

Mass spectrometric analysis of the fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts

The fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts were analyzed by gas liquid chromatography and combined gas liquid chromatographymass spectrometry. The fatty acids detected were identified as C_14∶0, C_16∶0, C_16∶1, C_18∶0, C_18∶1, and C_18∶2. Though the wt of the fatty acid fraction decreased during sporulation from 91 μg per 10⁶ oocysts to 47 μg per 10⁶ oocysts, the relative amounts of these fatty acids did not change appreciably. The nonsaponifiable lipids ofE. tenella consisted of cholesterol and unbranched primary alcohols of 22, 24, 26, 28, 30, and 32 carbons. Mass fragmentography demonstrated that each species of alcohol consisted of saturated and monounsaturated derivatives. Trimethylsilyl ethers of fatty alcohols were found to offer several important advantages over free alcohols for mass spectrometric characterization. Before sporulation, most fatty alcohols were in the oocyst wall. During sporulation, the wt of the nonsaponifiable lipids increased from 16 μg per 10⁶ oocysts of 44 μg per 10⁶ oocysts due largely to synthesis of C₂₄ and C₂₆ alcohols. The newly synthesized fatty alcohols were not deposited in the oocyst wall.     

Polyunsaturated fatty glyceride syntheses by microbial lipases

The degree of glyceride syntheses by lipase TOYO (Chromobacterium viscosum) and lipase OF (Candida cylindracea) using individual free fatty acids C_18∶1, C_18∶2, C_18∶3, C_18∶4, C_20∶4, C_20∶5 and C_22∶6 were compared. Lipase TOYO incorporated each of the fatty acids into glycerol at levels of greater than 89%. Lipase OF incorporated most of the fatty acids at levels above 70% (docosahexaenoic acid incorporation was 63%). It was concluded that these two lipases are feasible for producing glycerides from unsaturated fatty acids.     

Unsaturated fatty acids of mycobacteria

The double bond locations have been determined for the mono-unsaturated fatty acids, C₁₄ to C₂₆ ofM. smegmatis andM. bovis BCG. The 14∶1 and 16∶1 fatty acids fromM. smegmatis are principally Δ¹⁰, while the 17∶1, 18∶1 and 19∶1 fatty acids from both organisms are Δ⁹. In the case ofM. smegmatis, the 20∶1, 22∶1 and 24∶1 fatty acids are principally Δ¹¹, Δ¹³ and Δ¹⁵, respectively, while the 22∶1, 24∶1 and 26∶1 fatty acids of BCG are principally Δ¹³, Δ¹⁵ and Δ¹⁷, respectively.     

Comparative studies on the fatty acid composition of moderately and extremely thermophilic bacteria

The fatty acids of three strains of extremely thermophilic bacteria and three strains of moderately thermophilic bacteria were examined by gas liquid chromatography. All the thermophiles contained straight, iso, and ante-iso branched fatty acids. Iso C_17∶0 acid was abundant in both the moderately thermophilic strains (10–33%) and the extremely thermophilic strains (50–61%). The pair of fatty acids iso C_15∶0 and iso C_17∶0 was the predominant pair in both the moderately (34–64%) and extremely (76–87%) thermophilic strains. The pair of fatty acids ante-iso C_15∶0 and ante-iso C_17∶0 was present in larger amount in moderately (25–34%) than in extremely (8.5–15%) thermophilic strains. No hydroxy cyclopropane, or unsaturated fatty acids were found. One extreme thermophile,Flavobacterium thermophilum HB-8 was grown at 6 different culture temperatures from 49–82 C, and the changes of its fatty acid composition were studied. The ratios of iso C_17∶0/iso C_15∶0 and ante-iso C_17∶0/ante-iso C_15∶0 were much greater at higher culture temperatures, indicating chain elongation.     

Fatty acid composition of danish margarines and shortenings,with special emphasis ontrans fatty acids

Trans fatty acids from hydrogenated vegetable and marine oils could be as hypercholesterolemic and atherogenic as saturated fatty acids. Hence, it is important to know the fatty acid composition in major food contributors, e.g., margarines and shortenings. In 1992 margarines were examined, and in 1995 brands covering the entire Danish market were examined. Significant amounts oftrans-18∶1 were found only in hard margarines (mean: 4.2±2.8%) and shortenings (mean: 6.8 ±3.1%), whereas the semisoft and soft margarines contained substantially lesstrans-18∶1 in 1995 than in 1992. Where marine oils had been used to a larger degree the meantrans-monoenoic content was about 15%, of which close to 50% was made up of long-chain (C₂₀ and C₂₂)trans fatty acids. A note-worthy decrease in the content oftrans-18∶1 had occurred for the semisoft margarines, from 9.8±6.1% in 1992 to 1.2±2.2% in 1995. Calculated from sales figures, the supply oftrans-18∶1 plus saturated fatty acids from margarines had decreased over this three-year period by 1.4 g/day, which has been replaced bycis monounsaturated and polyunsaturated fatty acids.     

Fatty acids in the lipids ofDrosophila heads: Effects of visual mutants,carotenoid deprivation and dietary fatty acids

Lipids ofDrosophila heads were extracted and separated by high-performance thin-layer chromatography. Fatty acid compositions of major phospholipids as well as of triglycerides were analyzed by gas-liquid chromatography. Proportions of the major fatty acids (14∶0, 16∶0, 16∶1, 18∶0, 18∶1, 18∶2, 18∶3) varied depending on the lipid analyzed. Docosahexaenoic acid (22∶6), common in vertebrate photoreceptors and brain, and arachidonic acid (20∶4), a precursor of eicosanoids, were lacking. A comparison of the fatty acid composition of the dietvs. the head suggested thatDrosophila can desaturete but may not be able to elongate fatty acid carbon chains. Fatty acid analyses were carried out after the following visual system alterations: i) the transduction mutant whereno receptorpotential results from a deficit in phospholipase C; ii) an allele ofeyes absent; iii) the mutantouterrhabdomeresabsent which lacks visual pigment and rhabdomeres in the predominant type of compound eye receptor, rhabdomeres 1 through 6; and iv) carotenoid deprivation which reduces opsin and rhabdomere size. We also evaluated aging by comparing newly-emergedvs. aged wild-type flies. Alterations in fatty acid composition based on some of these manipulations were found. Based on comparisons between flies reared on media differing in C₁₆ and C₁₈, there is an indication that diet readily affects tissue fatty acid composition.     

Trans,n-3, and n-6 fatty acids in canadian human milk

The presence oftrans fatty acids in human milk may be a concern because of their possible adverse nutritional and physiological effects on the recipient infant. The mother's diet is the source of human milktrans fatty acids, and since these fatty acids are prevalent in many common foods of the Canadian diet, thetrans fatty acid content and the fatty acid composition of Canadian human milk were measured by gas-liquid chromatography coupled with silver nitrate-thin layer chromatography. In samples obtained from 198 lactating mothers across Canada, the average percentage of totaltrans (sum oft18∶1,t18∶2, andt18∶3) was 7.2% of breast milk fatty acids with a range of 0.1–17.2%. Analysis oft18∶1 isomer distribution indicated that partially hydrogenated vegetable oils are the major source of thesetrans fatty acids in human milk, whereas contribution from dairy products appeared to be relatively minor. Linoleci and α-linolenic acid levels were inversely related to the totaltrans fatty acids, indicating that the elevation oftrans fatty acids in Canadian human milk is at the expense of n-3 and n-6 essential fatty acids. Levels of arachidonic and docosahexaenoic acids did not correlate with their parent fatty acids, indicating that it might be difficult to elevate the levels of n-6 and n-3 C_20–22 polyunsaturated fatty acids in breast milk by increasing levels of linoleic and α-linolenic acids in the mother's diet.     

Essential fatty acid-deficient rats: II. On the fatty acid composition of partially hydrogenated arachis,soybean and herring oils and of normal,refined arachis oil

The fatty acid composition of partially hydrogenated arachis (HAO), partially hydrogenated soybean (HSO) and partially hydrogenated herring (HHO) oils and of a normal, refined arachis oil (AO) was studied in detail by means of direct gas liquid chromatography, ultraviolet and infrared spectrophotometry and by thin layer chromatography fractionation on silver nitrate-silica gel plates followed by gas liquid chromatography. It was shown that the partially hydrogenated oils all contained fatty acids withtrans double bonds. In the plant oils, thetrans acids were present mainly as elaidic acid. The HHO showed an almost equal distribution betweentrans 18∶1 ω9,trans 20∶1 ω>9 andtrans 22∶1 ω>9. Sometrans configuration was also found in the C₂₀-and C₂₂-dienes and trienes of the HHO. In all the oils, conjugated fatty acids were present in minor amounts only (<0.5%). Special attention was given to the ω-acids known to be of specific nutritional value. The HSO contained about 32% linoleic acid, whereas the content ofcis, trans+trans, cis andtrans, trans octadecadienoic isomers was 1.7% and 0.5%, respectively. The amount of linoleic acid in the HSO was even higher than that of AO (29%). The HAO contained only 0.8% 18∶2 ω6 (linoleic acid). Further, two 18∶2 fatty acids with ω>6, acis, cis and atrans, trans isomer, were present in small amounts. The HHO contained 0.5% 18∶2 ω6 (linoleic acid). Isomers of 18∶2 ω>6 were also found in the HHO. They may be hydrogenation products of higher unsaturated C₁₈-acids orginally present. All the C₂₀- and C₂₂-dienes and trienes were shown to have an ω-chain greater than 6. Fatty acids with ω6-structure were not formed during partial hydrogenation of the oils studied.     

The fatty acids ofEntomophthora coronata

The total lipids and fatty acid composition ofEntomophthora coronata were determined. The fungus was grown on a chemically defined medium and a chemically nondefined medium (Sabouraud dextrose yeast extract) for a period of 26 days. The organism contained from 16.2% to 44.6% total lipids depending upon the days of growth. The major fatty acids were 12∶0 (5.5–9.0%), 13∶0 (1.2–8.2%), 14∶0 (33.5–43.5%), 16∶0 (9.7–13.9%), 18∶1₉ (20.4–22.4%), and 18∶2_9,12 (3.5–10.5%). Lesser amounts of 15∶0, 16∶1, 16∶2, 17∶0, 18∶0, two other 18∶2 (both having conjugated double bonds), 18∶3_6,9,12, another 18∶3 (conjugated double bonds), 20∶3_8,11,14, 20∶4_5,8,11,14, another 20∶4 (conjugated double bonds), and 24∶1 acids were found. Trace amounts of 20∶0, 20∶1, 20∶2, 22∶0 and 24∶0 were also present. The relative percentage of most of the fatty acids did not vary appreciably with growth. However, 18∶2_9,12 and 20∶4_5,8,11,14 increased with age of the chemically defined culture. Peak E (18∶2, conjugated double bonds) increased and 13∶0 and 18∶3_6,9,12 decreased with age of the chemically nondefined culture. The fatty acids were predominately saturated (56.9–69.1%) and contained a high percentage of shorter chain fatty acids (C 12 to C 15). The fatty acids of the chemically defined culture were more unsaturated than the Sabouraud culture and the unsaturation increased with age of the culture.     

The effect of lyophilization on the solvent extraction of lipid classes,fatty acids and sterols from the oysterCrassostrea gigas

The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame-ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). The fatty acid methyl esters were separated using argentation TLC and also analyzed as their 4,4-dimethyloxazoline derivatives using GC/MS. Major esterified fatty acids inC. gigas were 16∶0, 20∶5n−3, and 22∶6n−3. C₂₀ and C₂₂ nonmethylene interrupted (NMI) fatty acids comprised 4.5 to 5.9% of the total fatty acids. The NMI trienoic fatty acid 22∶3(7,13,16) was also identified. Very little difference was found in the proportions of the various lipid classes, fatty acids or sterols between samples of adult oysters of two different sizes. However, significant differences in some of the lipid components were evident according to the method of sample preparation used prior to lipid extraction with solvents. Lyophilization (freeze drying) of samples led to a significant reduction in the amounts of triacylglycerols (TG) extracted by solvents in two separate experiments (7.0 and 52.5% extracted). Extracts from lyophilized samples had less 16∶0, C₁₈ unsaturated fatty acids, and 24-ethylcholest-5-en-3β-ol, while C₂₀ and C₂₂ unsaturated fatty acids comprised a higher proportion of the total fatty acids. There was no significant change in the amounts of polar lipids, total sterols, free fatty acids or hydrocarbons observed in extracts from lyophilized samples relative to extracts from nonlyophilized samples. Addition of water to the freezedried samples prior to lipid extraction greatly improved lipid yields and resulted in most of the TG being extracted.     

Fatty acid composition of rat hearts as influenced by age and dietary fatty acids

Fatty acid composition of neutral and polar lipid fractions from rat hearts was determined in rats of different ages as their diet source changed. Piebald rats were weaned at 21 days and were fed standard lab chow. Lipids from rat hearts, mothers milk and lab chow were purified on a Sephadex G-25 fine column and separated into neutral and polar lipid fractions by silicic acid column chromatography. These lipid fractions were then hydrolyzed and methylated with BF₃ in methanol, prior to gas liquid chromatographic separation on a 1/8 in. × 10 ft aluminum column of 15% EGS on 80–100 mesh acid-washed Chromosorb W. Three major fatty acids in the neutral lipid fraction comprised 72% of total neutral lipid fatty acids from young hearts. At sexual maturity (at least 74 days old) C_18∶1 was the major fatty acid, followed by C_16∶0 and C_18∶0. The same three fatty acids comprised 83% of total polar lipid fatty acids, but C_18∶0 was the major fatty acid, followed by C_16∶0 and C_18∶1. The fatty acid composition of dietary lipids influenced the total neutral lipid fatty acid composition of the rat heart, but had little influence on the fatty acid composition of the polar lipid fraction. Presented in part at the AOCS Meeting, New Orleans, April 1970.     

Biosynthesis of fatty acids byTrypanosoma cruzi

The incorporation of [1-¹⁴C] acetate into fatty acids by cultured epimastigotes ofTrypanosoma cruzi was studied. After 8, 24, and 48 hr incubation with labeled precursor, up to 2.8% of the initial radioactivity added to the medium was found in theT. cruzi long chain fatty acids. Saturated (16∶0 and 18∶0), monounsaturated (18∶1ω9), and diunsaturated (18∶2ω6) fatty acids were synthesized. Both the pattern of incorporation of labeled acetate into the fatty acids and the decarboxylation ratios found suggest that de novo synthesis of fatty acids has taken place.     

Norflurazon—An inhibitor of essential fatty acid desaturation in isolated liver cells

Norflurazon is a herbicide known to inhibit carotene biosynthesis and linolenic acid biosynthesis in plants. In the present work, the effect of norflurazon on the metabolism of essential fatty acids was studied in isolated rat liver cells and in rat liver microsomes, incubated with [1-¹⁴C] labeled linolenic acid (18∶3, n−3), dihomogammalinolenic acid (20∶3, n−6) and eicosapentaenoic acid (20∶5, n−3). Norflurazon (0.1 mM, 1.0 mM) was found to inhibit essential fatty acid desaturation. The Δ6 desaturation is inhibited more efficiently than the Δ5 and Δ4 desaturation. The chain elongation of essential C₁₈ fatty acids to their C₂₀ and C₂₂ homoglogs was not inhibited by norflurazon.     

Fatty acid metabolism in young oysters,Crassostrea gigas: Polyunsaturated fatty acids

Tetraselmis suecica andDunaliella tertiolecta were grown for 24 hr in the presence of¹⁴C sodium bicarbonate and then fed separately to batches of juvenile oysters,Crassostrea gigas, for 3 days.D. tertiolecta contained fatty acids no longer than C₁₈; 22∶6ω3 was absent inT. suecica. Analysis of the oyster fatty acids by radio gas chromatography (GC) showed that oysters were able to incorporate some of the dietary¹⁴C label into long-chain fatty acids not supplied in the diet, e.g., C₂₀ and C₂₂ mono- and polyunsaturated fatty acids, and particularly 20∶5ω3. However, the low¹⁴C incorporation into fatty acids longer or more unsaturated than those supplied in the diet suggests that elongation and desaturation activity in young oysters is not sufficient to sustain optimum growth.     

Arachidonic, eicosapentaenoic, and biosynthetically related fatty acids in the seed lipids from a primitive gymnosperm, Agathis robusta

The fatty acid composition of the seeds from Agathis robusta, an Australian gymnosperm (Araucariaceae), was determined by a combination of chromatographic and spectrometric techniques. These enabled the identification of small amounts of arachidonic (5,8,11,14–20∶4) and eicosapentaenoic (5,8,11,14,17–20∶5) acid for the first time in the seed oil of a higher plant. They were apparently derived from γ-linolenic (6,9,12–18∶3) and stearidonic (6,9,12,15–18∶4) acids, which were also present, via chain elongation and desaturation, together with other expected biosynthetic intermediates [bis-homo-γ-linolenic (8,11,14–20∶3) and bishomo-stearidonic (8,11,14,17–20∶4) acids]. Also present were a number of C₂₀ fatty acids, known to occur in most gymnosperm families, i.e., 5,11–20∶2, 11,14–20∶2 (bishomo-linoleic), 5,11,14–20∶3 (sciadonic), 11,14,17–20∶3 (bishomo-α-linolenic), and 5,11,14,17–20∶4 (juniperonic) acids. In contrast to most other gymnosperm seed lipids analyzed so far, A. robusta seed lipids did not contain C₁₈ Δ5-desaturated acids [i.e., 5,9–18∶2 (taxoleic), 5,9,12–18∶3 (pinolenic), or 5,9,12,15–18∶4 (coniferonic)]. These structures support the simultaneous existence of Δ6- and Δ5-desaturase activities in A. robusta seeds. The Δ6-ethylenic bond is apparently introduced into C₁₈ polyunsaturated acids, whereas the Δ5-ethylenic bond is introduced into C₂₀ polyunsaturated acids. A general metabolic pathway for the biosynthesis of unsaturated fatty acids in gymnosperm seeds is proposed. When compared to Bryophytes, Pteridophytes (known to contain arachidonic and eicosapentaenoic acids), and species from other gymnosperm families (without such acids), A. robusta appears as an “intermediate,” with the C₁₈ Δ6-desaturase/C₁₈→C₂₀ elongase/C₂₀ Δ5-desaturase system in common with the former subphyla, and the unsaturated C₁₈→C₂₀ elongase/C₂₀ Δ5-desaturase system specific to gymnosperms. The following hypothetical evolutionary sequence for the C₁₈ Δ6/Δ5-desaturase class in gymnosperm seeds is suggested: Δ6 (initial)→Δ6/Δ5 (intermediate)→Δ5 (final).     

trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist oftrans 20∶1 andtrans 22∶1 in addition to thetrans isomers of 18∶1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietarytrans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 dayspostpartum in sows. The dietary fats were PHFO (28%trans), or PHSBO (36%trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or “fully” hydrogenated fish oil (HFO) (19%trans), in comparison with coconut oil (CF) (0%trans), was fed with two levels of dietary linoleic acid, 1 and 2.7% from conception throughout the lactation period. Feedingtrans-containing fats led to secretion oftrans fatty acids in the milk lipids. Levels oftrans 18∶1 andtrans 20∶1 in milk lipids, as percentages of totalcis+trans 18∶1 andcis+trans 20∶1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively lesstrans 18∶1 andtrans 20∶1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels ofcis+trans 22∶1 were found in milk lipids. Feedingtrans-containing fat had no consistent effects on the level of polyenoic fatty acids but reduced the level of saturated fatty acids and increased the level ofcis+trans monoenoic fatty acids. Increasing the dietary level of linoleic acid had no effect on the secretion oftrans fatty acids but increased the level of linoleic acid in milk. The overall conclusion was that the effect of dietary fats containingtrans fatty acids on the fat content and the fatty acid composition of colostrum and milk in sows were moderate to minor.     

Long chain fatty acid deficits in brain myelin sphingolipids of undernourished rat pups

A restricted maternal dietary intake (40% of ad libitum intake) is known to cause myelin deficit that is accompanied by decreased amounts of individual phospholipids and sphingolipids in brain myelin of suckling rats. This communication reports the effects of the same nutritional stress on the fatty acid composition of brain myelin lipids. In myelin of 19-day-old normally fed rats, palmitate (16∶0), stearate (18∶0) and oleate (18∶1) accounted for 80–90% of all fatty acids in phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Maternal dietary restriction resulted in deficits of total fatty acid content, but did not affect the proportional distribution of individual fatty acids among phospholipids. By contrast, longer chain (22- and 24-carbon) fatty acids accounted for more than half the fatty acid content of myelin cerebroside and sulfatide from the 19-day-old control rat pups. In undernourished rats of that age, proportions of lignocerate (24∶0) and nervonate (24∶1) in cerebroside and sulfatide were 40–50% lower than those in control rats. This, together with higher proportions of 16∶0, 18∶0 and 18∶1 and a higher ratio of C₁₆−C₂₀ to C₂₂−C₂₄ in under-nourished than in control rats, suggests an impairment in fatty acid chain elongation. Ten days of nutritional rehabilitation failed to restore the fatty acid imbalances; however, after an additional 5 days of ad libitum feeding, the experimental and control values were similar. The undernutrition results in hypomyelination, which is characterized by a proportional decrease in lignoceric and nervonic acids of sphingolipids.     

The effects oftrans fatty acids on fatty acyl Δ5 desaturation by human skin fibroblasts

The effectiveness of different fatty acids as inhibitors of fatty acyl Δ5 desaturation activity in human skin fibroblasts has been investigated. When incubated with 2.25 μM [¹⁴C] eicosatrienoate (20∶3ω6) in otherwise lipid-free medium, these cells rapidly incorporate the radiolabeled fatty acid into cellular glycerolipids and desaturate it to produce both [¹⁴C] arachidonate and [¹⁴C] docosatetraenoate. The Δ5 desaturation activity can be enhanced by prior growth of the cells without serum lipids. Elaidate (9t–18∶1) is a potent inhibitor of Δ5 desaturation whiletrans-vaccenate (11t–18∶1) is virtually without effect. Oleate and linoleate are only mildly inhibitory. Linoelaidate (9t, 12t–18∶2) is more inhibitory than linoleate but significantly less effective than elaidate. The effects of elaidate can be readily overcome by increasing the concentration of exogenous eicosatrienoate. Studies with a variety oftrans monounsaturates of differing chain lengths indicate that the ω9trans fatty acids are potent inhibitors of Δ5 desaturation, while ω7trans fatty acids are relatively ineffective. Intact human fibroblasts could thus be important in characterizing novel fatty acids as selective inhibitors of arachidonate synthesis in vivo.     

Desaturation of fatty acids inTrypanosoma cruzi

Uptake and metabolism of saturated (16∶0, 18∶0) and unsaturated [18∶1(n−9), 18∶2(n−6), 18∶3(n−3)] fatty acids by cultured epimastigotes ofTrypanosoma cruzi were studied. Between 17.5 and 33.5% of the total radioactivity of [1-¹⁴C]labeled fatty acids initially added to the culture medium was incorporated into the lipids ofT. cruzi and mostly choline and ethanolamine phospholipids. As demonstrated by argentation thin layer chromatography, gas liquid chromatography and ozonolysis of the fatty acids synthesized, exogenous palmitic acid was elongated to stearic acid, and the latter was desaturated to oleic acid and 18∶2 fatty acid. The 18∶2 fatty acid was tentatively identified as linoleic acid with the first bond in the Δ9 position and the second bond toward the terminal methyl end. Exogenous stearic acid was also desaturated to oleic and 18∶2 fatty acid, while oleic acid was only converted into 18∶2. All of the saturated and unsaturated fatty acids investigated were also converted to a small extent (2–4%) into polyunsaturated fatty acids. No radioactive aldehyde methyl ester fragments of less than nine carbon atoms were detected after ozonolysis of any of the fatty acids studied. These results demonstrate the existence of Δ9 and either Δ12 or Δ15 desaturases, or both, inT. cruzi and suggest that Δ6 desaturase or other desaturases of the animal type are likely absent in cultured forms of this organism.