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.     

Conversion of palmitate to unsaturated fatty acids differs in a Neurospora crassa mutant with impaired fatty acid synthase activity

The Neurospora crassa cel (fatty acid chain elongation) mutant has impaired fatty acid synthase activity. The cel mutant requires exogenous 16:0 for growth and converts 16:0 to other fatty acids. In contrast to wild-type N. crassa, which converted only 42% of the exogenous [7,7,8,8-²H₄]16:0 that was incorporated into cell lipids to unsaturated fatty acids, cel converted 72%. In addition, cel contains higher levels of 18:3^δ9,12,15 than wild-type, and synthesizes two fatty acids, 20:2^δ11,14 and 20:3^δ11,14,17, found at only trace levels in wild-type. Thus, the Δ15-desaturase activity and elongation activity on 18-carbon polyunsaturated fatty acids are higher for cel than wild-type. This altered metabolism of exogenous 16:0 may be directly due to impaired flux through the endogenous fatty acid biosynthetic pathway, or may result from altered regulation of the synthesis of unsaturated fatty acids in the mutant.     

Lipid and fatty acid characterization and metabolism in the sea anemonePhymactis clematis (Dana)

Neutral lipid, phospholipids and fatty acids of the sea anemonePhymactis clematis from the south-west Atlantic were characterized and quantified in spring and autumn. Neutral lipids predominated over phospholipids in both seasons. Triacylglycerol and diacylglycerol ethers were the major lipids. In spring, an increase of esterified sterols was noted. The major fatty acids found were 22∶5ω3, 20∶5ω3 and 16∶0. The sea anemones were also incubated in vivo with either [1-¹⁴C]linoleate or [1-¹⁴C] α-linolenate for 2 hr. Isotope incorporation into lipids and their transformations into higher fatty acids were examined. Both precursors were incorporated into the lipids, mainly in triacylglycerols and mono-acylglycerols, while α-linolenate was also incorporated into phospholipids. The radioactive linoleate was elongated to 20∶2, 22∶2 and 24∶2 fatty acids, but not desaturated to 18∶3ω6. α-Linolenate was desaturated by Δ6 desaturase to 18∶4ω3. The specificity of Δ6-desaturase is discussed.     

Biosynthesis of fatty acids in cell-free homogenates of lactating gerbil mammary gland

Cell-free homogenates of lactating mammary gland of gerbils maintained on a diet of sunflower seed, guinea pig chow and oats (Diet 1) or a diet of guinea pig chow and oats (Diet 2) and of rats maintained on laboratory chow (Diet 3) were incubated with¹⁴C-labeled acetate, acetyl CoA or malonyl CoA aerobically. A large proportion of the¹⁴C from¹⁴C-acetate and¹⁴C-acetyl CoA incorporated into fatty acids by homogenates from gerbils on Diet 1 was in unsaturated compounds, particularly in 18-carbon and 20-carbon dienoic acids, compared to preparations from animals on Diets 2 or 3. The two radioactive dienoic acids were proven to be Δ^9,12 18∶2 and Δ^11,14 20∶2, and the latter was shown to be a direct elongation product of Δ^9,12 18∶2 by the substrate¹⁴C-acetyl CoA. In all experiments¹⁴C from¹⁴C-malonyl CoA was incorporated predominantly into 14∶0 and 16∶0, and very little incorporation occurred into unsaturated fatty acids in homogenates made either from gerbil or rat. Total fatty acids isolated from homogenates and from milk fat (fat floating on the centrifuged homogenates) of gerbils on Diet 1 had a higher proportion of 18∶2 than animals on the other two diets, a reflection of the large dietary intake of linoleic acid by gerbils on Diet 1. Under these conditions the amount of 18∶2 in the mammary gland had a significant effect on the products of the incubation.     

Biosynthesis of polyunsaturated fatty acids in the developing brain: I. Metabolic transformations of intracranially administered 1-14C linolenic acid

Thirteen-day old rats were given intracranial injections of 1-¹⁴C linolenic acid (allcis 9,12,15 octa decatrienoic acid) and were sacrificed after 8 hr. Analysis of brain fatty acids showed that 16∶0, 18∶0, 18∶1, 18∶3, 20∶3, 20∶4, 20∶5, 22∶5, and 22∶6 were labeled. The total fatty acid methyl esters were separated into classes according to degree of unsaturation on a AgNO₃∶SiO₂ impregnated plate. The bands were scraped off and the eluted fatty acids were first analyzed by radiogas liquid chromatography and then subjected to reductive ozonolysis to determine double bond position. The saturated acids, 16∶0, and 18∶0, as well as the mono-unsaturated 18∶1, must have been formed from radioactive acetate produced by β oxidation of the injected linolenate. Among the polyunsaturated fatty acids, the triene fraction was characterized and identified as 18∶3 ε3 (Δ^9,12,15), the starting material, and 20∶3 ω3 (Δ^11,14,17); the tetraene fraction was identified as 20∶4 ω3 (Δ^8,11,14,17); the pentaene fraction was identified as 20∶5 ω3 (Δ^5,8,11,14,17) and 22∶5 ω3 (Δ^{7,10,13,16,19}); and, finally, the hexaene fraction was shown to be 22∶6 ω3 (Δ^{4,7,10,13,16,19}). The biosynthesis of these ω3 family fatty acids in the brain in situ is discussed.     

Incorporation oftrans long-chain n−3 polyunsaturated fatty acids in rat brain structures and retina

During heat treatment, polyunsaturated fatty acids and specifically 18∶3n−3 can undergo geometrical isomerization. In rat tissues, 18∶3 Δ9c, 12c, 15t, one of thetrans isomers of linolenic acid, can be desaturated and elongated to givetrans isomers of eicosapentaenoic and docosahexaenoic acids. The present study was undertaken to determine whether such compounds are incorporated into brain structures that are rich in n−3 long-chain polyunsaturated fatty acids. Two fractions enriched intrans isomers of α-linolenic acid were prepared and fed to female adult rats during gestation and lactation. The pups were killed at weaning. Synaptosomes, brain microvessees and retina were shown to contain the highest levels (about 0.5% of total fatty acids) of thetrans isomer of docosahexaenoic acid (22∶6 Δ4c, 7c, 10c, 13c, 16c, 19t). This compound was also observed in myelin and sciatic nerve, but to a lesser extent (0.1% of total fatty acids). However, the ratios of 22∶6trans to 22∶6cis were similar in all the tissues studied. When the diet was deficient in α-linolenic acid, the incorporation oftrans isomers was apparently doubled. However, comparison of the ratios oftrans 18∶3n−3 tocis 18∶3n−3 in the diet revealed that thecis n−3 fatty acids were more easily desaturated and elongated to 22∶6n−3 than the correspondingtrans n−3 fatty acids. An increase in 22∶5n−6 was thus observed, as has previously been described in n−3 fatty acid deficiency. These results encourage further studies to determine whether or not incorporations of suchtrans isomers into tissues may have physiological implications. Presented in part at the 32nd International Conference on the Biochemistry of Lipids, 1991, Granada, Spain. Delta nomenclature (Δ) is used fortrans polyunsaturated fatty acids to specify the position and geometry of ethylenic bonds. Polyunsaturated fatty acids containingtrans double bonds are abbreviated giving the locations of thetrans double bonds only; e.g., 20∶5 Δ17t 20∶5 Δ5c,8c,11c,14c,17t; 22∶5 Δ19t, 22∶5 Δ7c,10c,13c,16c,19t; 22∶6 Δ19t 22∶6 Δ4c,7c,10c,13c,16c,19t.     

Biosynthesis of polyunsaturated fatty acids in the developing brain: II. Metabolic transformations of intracranially administered [3-14C] eicosatrienoic acid,evidence for lack of Δ8 desaturasedesaturase

[3-¹⁴C] Eicosatrienoic acid (Δ11,14,17) chemically synthesized from [1-¹⁴C] linolenic acid was injected intracranially into 14-day old rats and sacrificed 8 hr later. The analysis of brain fatty acids by radio-gas liquid chromatography before and after ozonolysis showed that the tetraene fraction consisted of a desaturated product, Δ5,11,17–20∶4, and its elongated product, Δ7,13,16,19–22∶4. Both of these products, with a combined total of 61% of the total radioactivity recovered in the tetraene fraction, contain a nonmethylene interrupted double bond system and, therefore, are unsuitable for further desaturation. The other two components, Δ6,9,12,15–18∶4 and Δ8,11,14,17–20∶4, must have been formed from Δ9,12,15–18∶3, formed by retroconversion of the starting material 20∶3, followed by desaturation and elongation. These results suggest a lack of Δ⁸ desaturase in the developing brain, leading to formation of Δ5,11,14,17–20∶4 rather than Δ8,11,14,17–20∶4. Howeve, the nonmethylene interrupted double bond isomer does not restrict chain elongation.     

Changes in fatty acid composition in plant tissues expressing a mammalian Δ9 desaturase

Plant tissues expressing a mammalian stearoyl-CoA Δ9 desaturase were reported to accumulate Δ9 hexadecenoic acid (16∶1), normally very minor in most plant tissues. The transgenic plants were thoroughly analyzed for alterations of individual lipids in different subcellular sites. Western blot analysis indicated that the animal desaturase was targeted to the microsomes. The Δ9 16∶1 was incorporated into both the sn-1 and sn-2 positions of all the major membrane lipids tested, indicating that the endoplasmic reticulum acyltransferases do not exclude unsaturated C₁₆ fatty acids from the sn-2 position. In addition to increases in monounsaturated and decreases in saturated fatty acids, accumulation of 16∶1 was accompanied by a reduction in 18∶3 in all the lipids tested except phosphatidylglycerol, and increases in 18∶2 in phospholipids. Total C₁₆ fatty acid content in the galactolipids of the transgenics was significantly higher than that in the control, but those in the phospholipids were unchanged. In transgenics, Δ11 18∶1 was detected in the sn-1 position of the lipids tested except phosphatidylinositol and phosphatidylserine. Introduction of the animal desaturase, controlled by a seed-specific phaseolin promoter, into soybean somatic embryo resulted in a significant reduction in saturated fatty acids. Such effects were greater in cotyledons than hypocotyl-radicles. This study demonstrated that the animal desaturase can be used to decrease the levels of saturated fatty acids in a crop plant.     

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.     

Serum cholesterol predictive equations with special emphasis on trans and saturated fatty acids. an analysis from designed controlled studies

The effects of dietary trans fatty acids on serum total and low density lipoprotein (LDL) cholesterol have been evaluated by incorporating trans fatty acids into predictive equations and comparing their effects with the effects of the individual saturated fatty acids 12∶0, 14∶0, and 16∶0. Trans fatty acids from partially hydrogenated soybean oil (TRANS V) and fish oil (TRANS F) were included in previously published equations by constrained regression analysis, allowing slight adjustments of existing coefficients. Prior knowledge about the signs and ordering of the regression coefficients was explicitly incorporated into the regression modeling by adding lower and upper bounds to the coefficients. The amounts of oleic acid (18∶1) and polyunsaturated fatty acids (18∶2, 18∶3) were not sufficiently varied in the studies, and the respective regression coefficients were therefore set equal to those found by Yu et al. [Yu, S., Derr, J., Etherton, T.D., and Kris-Etherton, P.M. (1995) Plasma Cholesterol-Predictive Equations Demonstrate That Stearic Acid Is Neutral and Monounsaturated Fatty Acids Are Hypocholesterolemic, Am. J. Clin. Nutr. 61, 1129–1139]. Stearic acid (18∶0), considered to be neutral, was not included in the equations. The regression analyses were based on results from four controlled dietary studies with a total of 95 participants and including 10 diets differing in fatty acid composition and with 30–38% of energy (E%) as fat. The analyses resulted in the following equations, where the change in cholesterol is expressed in mmol/L and the change in intake of fatty acids is expressed in E%: Δ Total cholesterol=0.01 Δ(12∶0)+0.12 Δ(14∶0)+0.057 Δ(16∶0)+0.039 Δ(TRANS F)+0.031 Δ(TRANS V)−0.0044 Δ(18∶1)−0.017 Δ(18∶2, 18∶3) and ΔLDL cholesterol =0.01 Δ(12∶0)+0.071 Δ(14∶0)+0.047 Δ(16∶0)+0.043 Δ(TRANS F)+0.025 Δ(TRANS V)−0.0044 Δ(18∶1)−0.017 Δ(18∶2, 18∶3). The regression analyses confirm previous findings that 14∶0 is the most hypercholesterolemic fatty acid and indicate that trans fatty acids are less hypercholesterolemic than the saturated fatty acids 14∶0 and 16∶0. TRANS F may be slightly more hypercholesterolemic than TRANS V or there may be other hypercholesterolemic fatty acids in partially hydrogenated fish oil than those included in the equations. The test set used for validation consisted of 22 data points from seven recently published dietary studies. The equation for total cholesterol showed good prediction ability with a correlation coefficient of 0.981 between observed and predicted values. The equation has been used by the Norwegian food industry in reformulating margarines into more healthful products with reduced content of cholesterol-raising fatty acids. These authors have contributed equally to this work.     

Desaturation of isomericcis 18∶1 acids

The desaturation of positionalcis 18∶1 isomers (Δ4 through Δ11) was studied, using essential fatty acid deficient rat liver microsomes. Thecis Δ4, Δ5, Δ6 and Δ7 isomers were not desaturated. Thecis Δ10 and Δ11 isomers were desaturated at a very low rate. The maximum desaturation was obtained for Δ8 and Δ9 isomers. Thecis Δ8 and Δ11 isomers were desaturated by Δ5 desaturase; thecis Δ9 isomer was desaturated by Δ6 desaturase; and thecis Δ10 isomer was desaturated to Δ7,10 and 5,10–18∶2 acids.     

Microbial Conversion of Vegetable Oil to Rare Unsaturated Fatty Acids and Fatty Alcohols by an <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis> Isolate

We isolated two new microorganisms capable of converting vegetable oil to several rare unsaturated fatty acids and rare unsaturated fatty alcohols from a soil sample. The strains were identified as belonging to the same genus and species, Aeromonas hydrophila. The rare unsaturated fatty acids and rare unsaturated fatty alcohols were accumulated as a wax ester form by the strains. Compared to other strains, the A. hydrophila isolates effectively decreased fatty acid chain lengths and converted rapeseed oil, which is rich in 9-C18:1 fatty acid, into rare fatty acids, such as 7-C16:1 fatty acid and 5-C14:1 fatty acid. Furthermore, the A. hydrophila isolates converted the resulting fatty acids to rare unsaturated fatty alcohols, such as 7-C16:1 fatty alcohol and 5-C14:1 fatty alcohol. The isolates also converted safflower oil, which is rich in 9,12-C18:2 fatty acid, to 7,10-C16:2 fatty acid, 5,8-C14:2 fatty acid, 9,12-C18:2 fatty alcohol, 7,10-C16:2 fatty alcohol, and 5,8-C14:2 fatty alcohol. 7,10,13-C16:3 fatty acid, 9,12,15-C18:3 fatty alcohol, and 7,10,13-C16:3 fatty alcohol were also converted from linseed oil, which is rich in 9,12,15-C18:3 fatty acid, by the A. hydrophila isolates. These fatty acids and fatty alcohols are rarely found in natural oils. Since decreasing fatty acid carbon chain lengths from the carboxyl end and reducing unsaturated fatty acids to unsaturated fatty alcohols are both difficult reactions to accomplish by chemical means, we suggest that these A. hydrophila isolates may facilitate introduction of new bioprocess for producing rare unsaturated fatty acids and rare unsaturated fatty alcohols, especially fatty alcohols harboring more than two double bonds.     

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 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.     

Biosynthesis of arachidonic acid in the oleaginous microalga Parietochloris incisa (Chlorophyceae): Radiolabeling studies

The fresh-water green alga Parietochloris incisa is the richest plant source of the PUFA arachidonic acid (20∶4n−6, AA). To elucidate the biosynthesis of AA in this alga we labeled cultures of P. incisa with radioactive precursors. Pulse chase labeling with acetate resulted in its incorporation via the de novo biosynthesis pathway of FA. However, labeled acetate was also utilized for the elongation of C₁₆ and C₁₈ PUFA. Labeling with [1-¹⁴C]oleic acid has shown that the first steps of the lipid-linked FA desaturations utilize cytoplasmic lipids. PC and diacylglyceryltrimethylhomoserine are the major lipids involved as acyl carriers for the Δ12 and Δ6 desaturations of oleic acid, leading sequentially to linoleic and γ-linolenic acids. The latter is released from its lipid carrier and elongated to 20∶3n−6, which is reincorporated primarily into PF and PC and finally desaturated to AA. Galactolipids, mostly monogalctosyldiacylglycerol (MGDG), serve as substrates for the chloroplastic Δ12 desaturase and, apparently, the ω3 desaturation, common to higher plants and many green algae. The predominant sequence desaturates the 18∶1/16∶0 molecular species of MGDG stepwise to the 18∶3n−3/16∶3n−3 molecular species similar to the prokaryotic pathway of higher plants and green algae.     

A comparison of the positional distribution of fatty acids in milk triglycerides of the extant monotremes platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus)

Milk triglycerides from the platypus were subjected to fatty acid and stereospecific analysis to determine the positional distribution of fatty acids in the triglycerides. Of the major fatty acids, 12∶0 was preferentially esterified at thesn-3 position, 14∶0 and 16∶0 were selectively associated with thesn-2 position, and 18∶0 was located predominantly at thesn-1 position. The unsaturated fatty acids, 14∶1, 16∶1, 18∶1, 18∶2 and 18∶3, were preferentially esterified at thesn-3 position. The fatty acid distribution pattern of the platypus, a monotreme, is similar to that of marsupials and eutherians but is in contrast to the only other extant monotreme, the echidna.     

Tissue culture of cocoa bean (Theobroma cacao L.): Incorporation of fatty acids into lipids of cultured cells

Suspension cell cultures of cocoa bean rapidly incorporated palmitic, stearic, oleic and linoleic acids into cellular lipids. Thus, 75 and 20% of [1-¹⁴C] palmitic acid was incorporated into polar lipids and triglycerides, respectively, after 48 hr. When [1-¹⁴C] oleic and [1-¹⁴C] linoleic acid were added separately, polar lipids consistently contained most of the radioactive fatty acids. Ca. 60% of the stearic acid accumulated as unesterified fatty acid in the cells. Palmitic and stearic acid were not desaturated, but oleic acid and linoleic acid were further desaturated. The kinetics of conversion of oleic acid and linoleic acid suggested a sequential desaturation pathway of 18∶1→18∶2→18∶3 in cocoa bean cell suspensions.     

Effect of different acids with Δ9,12-dienoic structures on Δ9 desaturation activity in rat liver microsomes

The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure on the fatty acid composition and Δ9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The ethyl esters of linoelaidic and γ-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic acid. The addition of linoleate or γ-linolenate to the fat-free diet returned liver microsome Δ9 desaturation activity toward the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18∶3), which cannot be transformed into arachidonic acid, also decreased the Δ9 desaturation activity enhanced by the fat-free diet and evoked changes in the microsomal fatty acid composition similar to those produced by the ω6 fatty acids. These results suggest that the modulation of Δ9 desaturase activity evoked by dietary administration of unsaturated acids of ω6 series would depend on thecis double bond configuration of these acids.     

Incorporation and distribution of saturated and unsaturated fatty acids into nuclear lipids of hepatic cells

Liver nuclear incorporation of stearic (18∶0), linoleic (18∶2n−6), and arachidonic (20∶4n−6) acids was studied by incubation in vitro of the [1-¹⁴C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-¹⁴C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18∶0>20∶4n−6≫18∶2n−6, and esterified into nuclear lipids by an acyl-CoA pathway. All [1-¹⁴C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols. Only [1-¹⁴C] 18∶2n−6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation of 20∶4n−6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-¹⁴C]20∶4n−6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined, five were labeled with [1-¹⁴C]20∶4n−6-CoA: 18∶0–20∶4, 16∶0–20∶4, 18∶1–20∶4, 18∶2–20∶4, and 20∶4–20∶4. The highest specific radioactivity was found in 20∶4–20∶4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell nuclei also utilize exogenous 20∶4n−6-CoA to synthesize the major molecular species of PC with 20∶4n−6 at the sn-2 position. However, the most actively synthesized is 20∶4–20∶4 PC, which is a quantitatively minor component. The labeling pattern of 20∶4–20∶4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway.     

Non-methylene-interrupted and ω4 dienoic fatty acids of the white shrimpPenaeus setiferus

The total lipid fatty acids from the white shrimpPenaeus setiferus were found to contain several unusual dienoic fatty acid species. These included two methylene-interrupted species: Δ11, 14-C_18∶2 (18∶2ω4) and δ13, 16-C_20∶2 (20∶2ω4). Also found were several non-methylene-interrupted dienoic fatty acids including δ7, 11 and Δ7, 13-C_20∶2, Δ7, 13-C_21∶2, Δ7, 13, Δ7, 15, Δ9, 13, Δ9, 15, and Δ7, 17-C_22∶2. Many minor C_20∶2 non-methylene-interrupted dienes were found but could not be unequivocally characterized.