A new view on the role of phospholipids fatty acids: Possibility of electric charge transfer in the membrane monolayer

The fatty acid composition of phospholipids of subcellular fractions that are both generators and consumers of energy, mitochondria, synaptosomes, and myelin, has been studied in the brain and liver of several representatives of poikilothermal and homoiothermal vertebrates. The terrestrial poikilothermal animals have been shown to be close to homoiothermal animals by the main characteristics of membranes of the subcellular fractions, such as the content of saturated acids, the unsaturation index, and the ω3/ω6 acid ratio, but differ essentially from aquatic poikilotherms. The conclusion is made that the similarity in the fatty acid characteristics of the terrestrial poikilothermal and homoiothermal vertebrate membranes is due to their inhabitation in the oxygen-rich environment, while differences in intensity of the oxygen consumption are due to their different body temperatures. The models of structure of an arbitrary fragment of the lipid component of the studied trout membranes are presented, which illustrate a concept of a new functional role of fatty acids as participants of the electron transfer chain in the membrane.     

The effects of maternal dietary treatments with natural PPAR ligands on lipid metabolism in fetuses from control and diabetic rats

Maternal diabetes impairs fetal development and growth. We studied the effects of maternal diets enriched in unsaturated fatty acids capable of activating peroxisome proliferator-activated receptors (PPARs) on the concentrations of 15deoxyΔ^12,14PGJ₂ (15dPGJ₂), lipid mass, and the de novo lipid synthesis in 13.5-day fetuses from control and diabetic rats. Diabetes was induced by neonatal streptozotocin administration (90 mg/kg). Rats were treated with a standard diet supplemented or not with 6% olive oil or 6% safflower oil from days 0.5 to 13.5 of gestation. Fetuses from diabetic rats fed with the standard diet showed reduced 15dPGJ₂ concentrations, whereas maternal treatments with olive and safflower oils increased 15dPGJ₂ concentrations. Fetuses from diabetic rats showed increased concentrations of phospholipids and increased synthesis of triglycerides, phospholipids, cholesterol and free fatty acids. Diabetic rat treatments with olive and safflower oils reduced phospholipids, cholesterol, and free fatty acid concentrations and the de novo lipid synthesis in the fetuses. These effects were different from those observed in fetuses from control rats, and seem not to involve PPARγ activation. In conclusion, olive oil- and safflower oil-supplemented diets provide beneficial effects in maternal diabetes, as they prevent fetal impairments in 15dPGJ₂ concentrations, lipid synthesis and lipid accumulation.     

Fatty acid and lipid analysis of the house cricket,Acheta domesticus

The fatty acid content and composition of the house cricket Acheta domesticus have been investigated in entire insects at different developmental stages and in selected organs of male and female adults. We have also determined the fatty acid composition of the various lipid classes within extracts of the organs of adult female insects. Fatty acids were analysed by capillary gas chromatography or mass spectrometry as their methyl esters (FAMEs) after direct transesterification of insect material or separated lipid classes.The major esterified fatty acids in all extracts were palmitate (C_16:0), stearate (C_18:0), oleate (C_18:1) and linoleate (C_18:2). Levels of esterified fatty acid varied considerably between organs but the fatty acid compositions showed only small variations. The levels of polyunsaturated fatty acids of the C₁₈ series were considerably higher in phospholipid fractions than in other lipid classes. Triacylglycerols formed the major lipid class in ovaries, fat-body and newly-laid eggs, whereas diacylglycerols and phospholipid predominate in the haemolymph. Triacylglycerols, phospholipids, diacylglycerols and free fatty acids were all found in significant amounts in the gut tissue.     

Mechanisms of lipid peroxidation in erythrocytes of vitamin E-deficient rats and in phospholipid model systems

Erythrocytes from vitamin E-deficient and control rats were peroxidized by glucose oxidase-glucose or dialuric acid. Losses of polyunsaturated fatty acids from membrane phospholipids, and of dimethylacetals from plasmalogens, were quantitated by gas-liquid chromatography. Similar treatment of solubilized or micellar phospholipids or plasmalogens in vitro showed that in both erythrocytes and micellar systems, arachidonic acid and the 16-carbon plasmalogen are most susceptible to peroxidation by either reagent. The same narrow concentration range of dialuric acid found effective in peroxidizing erythrocytes from tocopherol-deficient rats was also found effective in peroxidizing micellar phospholipids in vitro.Partially peroxidized erythrocytes from tocopherol-deficient rats were subjected to treatment with phospholipase A or phospholipase C. Hemolysis by either phospholipase was accelerated in partially peroxidized cells as compared to controls, suggesting that peroxidation exposes both polar and nonpolar lipid sites in the erythrocyte membrane.     

Peculiarities of Ultraviolet Absorption Spectra of Lamprey and Rat Brain Lipid Extracts and Their Correlation with Fatty Acid Composition

The ultraviolet (UV) absorption spectra of rat and lamprey brain lipid extracts have been studied. It was found that in both species the absorption of UV light took place, the shift of the absorption spectra to the more long-wave region being observed in the lamprey brain lipid extract. The established fact indicate the presence of oxidation products of lipids and their diene conjugates in the studied extracts, i.e., the appearance of the conjugated system of unsaturated bonds in the phospholipid molecules. The shift of the spectra to the more long-wave region in lampreys indicates a possible difference in the amount of polyenoic fatty acids in lamprey phospholipids. It was found that in lampreys it is predominantly the products of oxidation of phosphotidylcholine fatty acids, which shift the absorption spectrum to the more long-wave region. These are docosahexaenoic (C22:6 3), docosapentaenoic (C22:5 3), and eicosapentaenoic acids (C20:5 3). It is suggested that the membrane construction itself provides the basis for the energy accumulation.     

Effect of Biotin on Fatty Acids and Phospholipids of Biotin-Sensitive Strains of Rhizobium japonicum

The effect of biotin on fatty acids and intact lipids was studied by comparing a biotin-requiring, a biotin-inhibited, and a biotin-indifferent strain of Rhizobium japonicum. These organisms were grown in a defined medium with added levels of 0, 0.3, and 0.5 μg of biotin per liter, and were analyzed for fatty acids and lipid components. Myristic, palmitic, and octadecenoic acids were found to be the major fatty acids in these strains. The indifferent strain also contained large amounts of C₁₉ cyclopropane acid and small amounts of a C₁₇ cyclopropane acid. Several unidentified acids were present in the other two strains. The percentages of fatty acids showed statistically significant changes corresponding with changes in level of biotin in the medium. When biotin concentration was increased in the medium, the C₁₈ monoenoic acids of the biotin-requiring strain increased significantly, and those of the biotin-inhibited and biotin-indifferent strains decreased significantly. Palmitic acid showed a statistically significant increase in the indifferent strain with increasing biotin concentration. The principal intact lipid components in these strains are phospholipids. The major phospholipids are phosphatidylserine, phosphatidylcholine, phosphatitidylethanolamine, and cardiolipin. These phospholipids were not affected by biotin level and were independent of medium composition.     

Changes in the Amount of Complex Lipids in the Seeds and in the Pericarp during the Development of Ivy Fruit (Hedera helix)

By a combination of thin-layer chromatography and gas liquid chromatography, a complete study of the development of the different lipid classes and of their fatty acids, during the development of the fruit of Hedera helix L., the English Ivy, has been achieved. In any part of the fruit observed, at any particular stage, the phospholipids and the neutral lipids are the most abundant lipid classes. They accumulate during the entire process of maturation, whereas significant changes occur in their relative proportions, phospholipids being largely dominant until fruit blackening. The accumulation of fatty acids during maturation is characterized by large amounts of C_18:1 in the neutral lipids, especially in the seed, where petroselinic acid (C_18:1Δ⁶) reaches 86% of the total fatty acids. To a smaller extent, the phospholipids also accumulate and thus have the character of reserve molecules. However, their composition remains more stable, which relates them to the “structural lipids” such as galactolipids that maintain their characteristic fatty acid composition, despite the radical changes occurring in the fatty acid metabolism during fruit ripening.     

Selectivity of phospholipid hydrolysis by phospholipase A2 enzymes in activated cells leading to polyunsaturated fatty acid mobilization

Phospholipase A₂s are enzymes that hydrolyze the fatty acid at the sn-2 position of the glycerol backbone of membrane glycerophospholipids. Given the asymmetric distribution of fatty acids within phospholipids, where saturated fatty acids tend to be present at the sn-1 position, and polyunsaturated fatty acids such as those of the omega-3 and omega-6 series overwhelmingly localize in the sn-2 position, the phospholipase A₂ reaction is of utmost importance as a regulatory checkpoint for the mobilization of these fatty acids and the subsequent synthesis of proinflammatory omega-6-derived eicosanoids on one hand, and omega-3-derived specialized pro-resolving mediators on the other. The great variety of phospholipase A₂s, their differential substrate selectivity under a variety of pathophysiological conditions, as well as the different compartmentalization of each enzyme and accessibility to substrate, render this class of enzymes also key to membrane phospholipid remodeling reactions, and the generation of specific lipid mediators not related with canonical metabolites of omega-6 or omega-3 fatty acids. This review highlights novel findings regarding the selective hydrolysis of phospholipids by phospholipase A₂s and the influence this may have on the ability of these enzymes to generate distinct lipid mediators with essential functions in biological processes. This brings a new understanding of the cellular roles of these enzymes depending upon activation conditions.     

Characterization of gastric mucosal membranes: lipid composition of purified gastric microsomes from pig, rabbit, and frog

The lipid compositions of the gradient-purified gastric microsomal membranes from the fundic mucosa of pig, rabbit, and frog were determined. The total lipid content varied widely. Compared to the rabbit (21.6 ± 0.6 mg/100 mg protein), the pig had about twice as much and the frog about three times as much lipid. The levels of cholesterol were higher in both mammalian species (about 32% of the lipid) compared to frog (23%). Phospholipids accounted for about 45, 54, and 52% of the total microsomal lipids from pig, rabbit, and frog and the molar ratios of cholesterol to phospholipid in the three species were 1.95, 1.6, and 1.17, respectively. Phosphatidyl choline and phosphatidyl ethanolamine together constituted about 75% of the total phospholipids in pig and frog and 93% in rabbit gastric microsomes. Sphingomyelin comprised 19.3, 3.2, and 1.5% in pig, rabbit, and frog, respectively. Phosphatidyl inositol constituted 5, 2.7, and 23.6% in pig, rabbit, and frog, respectively. The ratios of phosphatidyl ethanolamine to phosphatidyl choline were 1.17, 1.1, and 0.85 in pig, rabbit, and frog, respectively. The saturated fatty acids 16:0 and 18:0 and the unsaturated fatty acid 18:1 and 18:2 were the predominant fatty acids in all phospholipids. The ratios of saturated to unsaturated fatty acids were between 0.8 and 0.9 in phosphatidyl choline and 0.27 and 0.5 in phosphatidyl ethanolamine from all three species. The contributions by saturated fatty acids were much more in phosphatidyl inositol and sphingomyelin than in phosphatidyl choline and phosphatidyl ethanolamine from all species. Position 1 of phosphatidyl choline had 63% saturated and 37% unsaturated fatty acids; while the reverse was true for position 2. Phosphatidyl ethanolamine, however, had 85% saturated fatty acids in position 1 compared to only 25% in position 2. Arachidonic acid (20:4) was present in significant amounts in all species located exclusively at position 2 of both phosphatidyl choline and phosphatidyl ethanolamine.     

Effect of total hypothermia on the fatty acid composition of blood phospholipids of rats and ground squirrels and of the light irradiation on chemical processes in lipid extract

Effect of hypothermia on the fatty acid composition of rat and ground squirrel blood phospholipids is studied. Different reaction of these animals to cooling is revealed; in rats no changes were observed in the fatty acid composition of blood phospholipids, whereas in the winterhibernating ground squirrels there were significant changes in the content of individual fatty acids (FA). The content of monoenic acids in ground squirrels decreased almost by 50%, while the content of saturated acid (C18) and of polyenic acids C18: 2ω6 and C20: 4ω6 rose significantly. Such changes seem to be the mechanism that promotes maintenance of the organism viability under conditions of a decreased level of metabolism, heart rhythm, and body temperature and is evolutionary acquired. At the same time, the observed changes in the content of individual FA do not lead to sharp changes in such integrative parameters as the total non-saturation of phospholipids, which determines liquid properties of chylomicrons and other lipolipoprotein transport particles of the ground squirrel blood. There are studied absorption spectra of blood lipid extracts of rats and ground squirrels under effect of light as well as effect of light upon the FA composition of lipid extracts of these animals. The FA composition of lipid extracts has been established to remain practically constant, whereas the character of changes of spectra under action of light indicates the presence in the extracts of oxidation-reduction reactions. The obtained data allow suggesting that in the lipid extract there occurs cooperation of both the phospholipids molecules themselves and of them with other organic molecules, which makes it possible for fatty acids to participate in processes of transport both of electrons and of protons. This novel role of FA as a participant of the electron transfer might probably be extrapolated to chemical reactions (processes) occurring inside the membrane.     

Photosynthesis,lipids and proteins in the cyanobacteriumSynechocystis PCC 6803 as affected by temperature

The cyanobacteriumSynechocystis PCC 6803 was grown photoautotrophically in an inorganic medium at constant growth temperatures of 20, 38 (control) or 43°C for 9 h. The up and down-shift of cultivation temperature decreased the growth as measured by culture absorbance and chlorophylla content. However, high temperature slightly increased the oxygen evolution while temperature lower than control inhibited oxygen evolution during the whole incubation period. The protein synthesis studied by¹⁴C-labeled protein declined under low temperature by about 50%. The fatty acid pattern is characterized as lacking in C₂₀/C₂₂ acids but containing large amounts of C₁₆ and C₁₈ polyunsaturated fatty acids, 16:2 and 18:3 in particular. The lower temperature increased the percentage of monounsaturated fatty acids while higher temperature increased the saturated fatty acid content in total lipids and lipid classes studied.     

The effects of maternal dietary treatments with natural PPAR ligands on lipid metabolism in fetuses from control and diabetic rats

Maternal diabetes impairs fetal development and growth. We studied the effects of maternal diets enriched in unsaturated fatty acids capable of activating peroxisome proliferator-activated receptors (PPARs) on the concentrations of 15deoxyΔ^12,14PGJ₂ (15dPGJ₂), lipid mass, and the de novo lipid synthesis in 13.5-day fetuses from control and diabetic rats. Diabetes was induced by neonatal streptozotocin administration (90 mg/kg). Rats were treated with a standard diet supplemented or not with 6% olive oil or 6% safflower oil from days 0.5 to 13.5 of gestation. Fetuses from diabetic rats fed with the standard diet showed reduced 15dPGJ₂ concentrations, whereas maternal treatments with olive and safflower oils increased 15dPGJ₂ concentrations. Fetuses from diabetic rats showed increased concentrations of phospholipids and increased synthesis of triglycerides, phospholipids, cholesterol and free fatty acids. Diabetic rat treatments with olive and safflower oils reduced phospholipids, cholesterol, and free fatty acid concentrations and the de novo lipid synthesis in the fetuses. These effects were different from those observed in fetuses from control rats, and seem not to involve PPARγ activation. In conclusion, olive oil- and safflower oil-supplemented diets provide beneficial effects in maternal diabetes, as they prevent fetal impairments in 15dPGJ₂ concentrations, lipid synthesis and lipid accumulation.     

Fatty acids of rice coleoptiles in air and anoxia

The metabolism of lipids, like that of other components, was adversely and strongly affected when rice (Oryza sativa L.) coleoptiles were grown anaerobically. In aerobic coleoptiles, the amounts of total fatty acid, phospholipid, and total lipid per coleoptile increased by 2.5- to 3-fold between days three and seven, whereas under anoxia, the increases were all less than 60%. The total amount of lipid at day seven in anoxia was less than 30% of that in air. In air, the total fatty acid content at day three was 25 nanomoles per coleoptile and this increased to over 71 nanomoles per coleoptile at day seven. All acids except 18:0 showed substantial increases. In anoxia, the corresponding values for total fatty acids were 24 nanomoles and 27 nanomoles. The small increases were confined to the saturated fatty acids; no significant increase occurred in unsaturated fatty acids. A minor fatty acid constituent (16:1) increased from 0.09 to 1.99 nanomoles per coleoptile between days three and seven in air. This component was never observed in any fatty acid preparation from anaerobic coleoptiles. The major phospholipids under all conditions were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidic acid. A small amount of unidentified phosphoester, not present on thin layer chromatography plates from aerobic coleoptiles, was seen in extracts of anaerobic coleoptiles. The fatty acyl substituents of each of the phospholipids were analyzed at days three and seven in coleoptiles grown aerobically and in anoxia. Each phospholipid had its own distinctive fatty acid composition which remained fairly constant under all treatments; 16:0 and 18:2 were the most abundant fatty acids in every phospholipid class. In air, the percentages of total fatty acids that were in the phospholipids were 86% on day three and 87% on day seven. In anoxia, the values at the corresponding ages were 47 and 57%. Since no net synthesis of unsaturated fatty acids occurred in anaerobic conditions, the small increase in total unsaturated acids in the phospholipids between days three and seven must have occurred at the expense of fatty acids preexisting in the neutral lipid. No unusual pathways of biosynthesis or unusual precursors are required to explain the presence of unsaturated fatty acids in the rice coleoptile. The present study and results of experiments where coleoptiles were fed [¹⁴C]acetate (BB Vartapetian et al. 1978 Plant Sci Lett 13:321-328) clearly show that unsaturated fatty acid synthesis in rice coleoptiles requires O₂, as it does in other plants.     

Impact of oxygen stress and energy availability on membrane stability of plant cells

This article reviews the relationship between the energy status of plant cells under O₂ stress (e.g. waterlogging) and the maintenance of membrane intactness, using information largely derived from suspension cultures of anoxia‐intolerant potato cells. Energy‐related parameters measured were fermentation end‐products (ethanol, lactate, alanine), respiratory rate, ATP, adenylate energy charge, nitrate reductase activity and biomass. ATP synthesis rates were calculated from the first four parameters. Reactive oxygen species were estimated from H₂O₂ and superoxide levels, and the enzymatic detoxification potential from the activity levels of catalase and superoxide dismutase. Structure‐related parameters were total fatty acids, free fatty acids (FFAs), lipid hydroperoxides, total phospholipids, N‐acylphosphatidylethanolamine (NAPE) and cell viability. The following issues are addressed in this review: (1) what is the impact of anoxia on membrane lipids and how does this relate to energy status; (2) does O₂ per se play a role in these changes; (3) under which conditions and to what extent does lipid peroxidation occur upon re‐aeration; and (4) can the effects of re‐aeration be distinguished from those of anoxia? The emerging picture is a reappraisal of the relative contributions of anoxia and re‐aeration. Two successive phases (pre‐lytic and lytic) characterize potato cells under anoxia. They are connected by a threshold in ATP production rate, below which membrane lipids are hydrolysed to FFAs, and NAPE increases. Since lipid peroxidation occurs only when cells are reoxygenated during the lytic phase, its biological relevance in an already damaged system is questionable.Key words: Acorus calamus L., energy shortage, free fatty acids, lipid peroxidation, lipolytic acyl hydrolase, lipoxygenase, membrane intactness, N‐acylphosphatidylethanolamine, O₂ stress, reactive oxygen species, Solanum tuberosum L.     

Tissue polyunsaturated fatty acids and a digestive phospholipase A2 in the primary screwworm,Cochliomyia hominivorax

We report on the presence of arachidonic acid in larval and adult tissues of the primary screwworm, Cochliomyia hominivorax and of the secondary screwworm, C. macellaria. Arachidonic acid is present in the phospholipids of whole animal extracts of both species. This fatty acid appears to be accumulated during the larval stages, because proportions of arachidonic acid were higher in adults than in larvae. These insects probably obtain the arachidonic acid from dietary phospholipids. We also report on a phospholipase A₂ activity in midgut preparations from third instars of the primary screwworm. Phospholipase A₂ is responsible for hydrolyzing fatty acids from the sn-2 position of dietary phospholipids to release essential fatty acids. The screwworm enzyme is similar to mammalian digestive phospholipase A₂s because it depends on calcium for high catalytic activity, it is sensitive to the site-specific inhibitor oleyloxyethylphosphorylcholine, and it interacts with heparin. We further characterized the screwworm midgut phospholipase A₂ by altering the reaction conditions, including reaction time, radioactive substrate concentration, protein concentration, pH and temperature. We speculate that the biological significance of this enzyme relates to acquiring essential fatty acids, including arachidonic acid, from dietary phospholipids.     

Specific oxygenation of plasma membrane phospholipids by Pseudomonas aeruginosa lipoxygenase induces structural and functional alterations in mammalian cells

Pseudomonas aeruginosa is a gram-negative pathogen, which causes life-threatening infections in immunocompromized patients. These bacteria express a secreted lipoxygenase (PA-LOX), which oxygenates free arachidonic acid to 15S-hydro(pero)xyeicosatetraenoic acid. It binds phospholipids at its active site and physically interacts with lipid vesicles. When incubated with red blood cells membrane lipids are oxidized and hemolysis is induced but the structures of the oxygenated membrane lipids have not been determined. Using a lipidomic approach, we analyzed the formation of oxidized phospholipids generated during the in vitro incubation of recombinant PA-LOX with human erythrocytes and cultured human lung epithelial cells. Precursor scanning of lipid extracts prepared from these cells followed by multiple reaction monitoring and MS/MS analysis revealed a complex mixture of oxidation products. For human red blood cells this mixture comprised forty different phosphatidylethanolamine and phosphatidylcholine species carrying oxidized fatty acid residues, such as hydroxy-octadecadienoic acids, hydroxy- and keto-eicosatetraenoic acid, hydroxy-docosahexaenoic acid as well as oxygenated derivatives of less frequently occurring polyenoic fatty acids. Similar oxygenation products were also detected when cultured lung epithelial cells were employed but here the amounts of oxygenated lipids were smaller and under identical experimental conditions we did not detect major signs of cell lysis. However, live imaging indicated an impaired capacity for trypan blue exclusion and an augmented mitosis rate. Taken together these data indicate that PA-LOX can oxidize the membrane lipids of eukaryotic cells and that the functional consequences of this reaction strongly depend on the cell type.     

Correlation between the Lipid Composition and the Responsiveness of Avena sativa Stem Segments to Gibberellic Acid

The lipid composition of Avena sativa stem segments was manipulated using BASF 13-338 (formerly Sandoz 9785) and growth temperature, in order to establish whether there were correlations between responsiveness of the tissue to gibberellic acid (GA₃) and the presence, before hormone treatment, of specific lipid components. High correlations were obtained between GA₃-induced growth and total phospholipid, individual phospholipids, and fatty acids (except for linolenic acid), total saturated fatty acids, stigmasterol content, and the unsaturated/saturated fatty acid ratio. It was concluded that, although the lipid composition, and particularly the total saturated fatty acid content, seem to be important contributory determinants of the GA₃-induced growth response in this system, they may not be obligatory prerequisites, nor the only endogenous factors capable of influencing the response. However, the results are consistent with the hypothesis that membranes are involved in the hormonal mechanism and/or very early stages of the mode of GA₃ action in this tissue.     

Lipid and Fatty Acid Composition in the Flesh of an Edible Marine Fish: Amadi (Coilia reynaldi)

Amadi is a small sized edible marine fish species (Coilia reynaldi) under the order-Clupeiformes. It is important for principal lipids and in particular for highly unsaturated fatty acids which have potential biomedical benefits. Among the lipid classes, phospholipids were found to be the most predominant constituents than the glycolipid and neutral lipid in Amadi. Twenty six fatty acids were quantified by open tube gas–liquid chromatography. Dominant fatty acids in this fish are Palmitic acid (C_16:0), Stearic acid (C_18:0), Oleic acid (C_18:1n?9), Myristic acid (C_14:0), Palmitoleic acid (C_16:1), Docosahexanoic acid (C_22:6n?3), Pentadecanoic acid (C_15:0), and Eicosatetraenoic acid (C_20:4n?3). Fatty acid deficiency in fish species is indicated by the presence of C_20:3n?9 acid. It is absent in this fish.The content of DHA and EPA are maximum in amount in neutral lipid than other lipid classes.     

Schistosoma mansoni does not and cannot oxidise fatty acids,but these are used for biosynthetic purposes instead

Adult schistosomes, parasitic flatworms that cause the tropical disease schistosomiasis, have always been considered to be homolactic fermenters and, in their energy metabolism, strictly dependent on carbohydrates. However, more recent studies suggested that fatty acid β-oxidation is essential for egg production by adult female Schistosoma mansoni. To address this conundrum, we performed a comprehensive study on the lipid metabolism of S. mansoni. Incubations with [¹⁴C]-labelled fatty acids demonstrated that adults, eggs and miracidia of S. mansoni did not oxidise fatty acids, as no ¹⁴CO₂ production could be detected. We then re-examined the S. mansoni genome using the genes known to be involved in fatty acid oxidation in six eukaryotic model reference species. This showed that the earlier automatically annotated genes for fatty acid oxidation were in fact incorrectly annotated. In a further analysis we could not detect any genes encoding β-oxidation enzymes, which demonstrates that S. mansoni cannot use this pathway in any of its lifecycle stages. The same was true for Schistosoma japonicum and all other schistosome species that have been sequenced. Absence of β-oxidation, however, does not imply that fatty acids from the host are not metabolised by schistosomes. Adult schistosomes can use and modify fatty acids from their host for biosynthetic purposes and incorporate those in phospholipids and neutral lipids. Female worms deposit large amounts of these lipids in the eggs they produce, which explains why interference with the lipid metabolism in females will disturb egg formation, even though fatty acid β-oxidation does not occur in schistosomes. Our analyses of S. mansoni further revealed that during the development and maturation of the miracidium inside the egg, changes in lipid composition occur which indicate that fatty acids deposited in the egg by the female worm are used for phospholipid biosynthesis required for membrane formation in the developing miracidium.