Significance of non-esterified fatty acids in iron uptake by intestinal brush-border membrane vesicles

Iron uptake from Fe/ascorbate by mouse brush-border membrane vesicles is not greatly inhibited by prior treatment with a variety of protein-modification reagents or heat. Non-esterified fatty acid levels in mouse proximal small intestine brush-border membrane vesicles show a close positive correlation with initial Fe uptake rates. Loading of rabbit duodenal brush-border membrane vesicles with oleic acid increases Fe uptake. Depletion of mouse brush-border membrane vesicle fatty acids by incubation with bovine serum albumin reduces Fe uptake. Iron uptake by vesicles from Fe/ascorbate is enhanced in an O2-free atmosphere. Iron uptake from Fe/ascorbate and Fe3+-nitrilotriacetate (Fe3+-NTA) were closely correlated. Incorporation of oleic acid into phosphatidylcholine/cholesterol (4:1) liposomes leads to greatly increased permeability to Yb3+, Tb3+, Fe2+/Fe3+ and Co2+. Ca2+ and Mg2+ are also transported by oleic acid-containing liposomes, but at much lower rates than transition and lanthanide metal ions. Fe3+ transport by various non-esterified fatty acids was highest with unsaturated acids. The maximal transport rate by saturated fatty acids was noted with chain length C14-16. It is suggested that Fe transport can be mediated by formation of Fe3+ (fatty acid)3 complexes.     

Cholate-soluble and -insoluble iron binding components of rabbit duodenal brush-border membrane. Relevance to Fe2+ uptake by brush-border membrane vesicles

Fe2+ uptake by brush-border membrane vesicles from rabbit duodenum has been investigated and found to show similar qualitative properties to those previously demonstrated with mouse proximal intestine brush-border membrane vesicles (Simpson, R.J. and Peters, T.J. (1986) Biochim. Biophys. Acta 856, 109-114). In particular, a relatively low affinity (Km(app) approx. 83 microM), NaCl and pH sensitive transport component is present. The disruption of 59Fe2+-laden vesicles with sodium cholate, followed by gel filtration or centrifugal analysis reveals that cholate insoluble material (Mr greater than 10(6)) is the major destination for 59Fe2+ taken up by intact vesicles. Analysis of cholate extracts for Fe2+ binding ability reveals a single high-capacity (49.8 +/- 15.6 nmol/mg vesicle protein (S.E., n = 3)), high-affinity (Kd(app) less than 5 microM) binding component with an Mr equivalent to approx. 10(4) on gel filtration in the presence of cholate. This binding component is extracted into chloroform/methanol (2:1, v/v) is relatively heat and protease resistant and thus appears to be a lipid.     

Fe3+ transport by brush-border membrane vesicles isolated from normal and hypoxic mouse duodenum and ileum

Studies of 59Fe3+ uptake by brush-border membrane vesicles prepared from mouse duodenum have indicated that uptake represents transport across the brush-border membrane which is rate-limited by the membrane-transfer step (Simpson, R.J. and Peters, T.J. (1984) Biochim. Biophys. Acta 772, 220-226). Further studies presented here reveal that the uptake rate represents the net influx rate for Fe3+ and is independent of Na+ in the medium and of the method of vesicle preparation. Uptake by brush-border membrane vesicles prepared from mouse distal ileum also represents predominantly transport and is higher than that observed with duodenal brush-border membrane vesicles. Studies of the initial uptake rate by vesicles prepared from normal and hypoxic mouse intestine demonstrated an increase in Fe3+ transport in duodenal vesicles only.     

Enzymatic removal of alkaline phosphatase from renal brush-border membranes. Effect on phosphate transport and on phosphate binding

Brush-border membrane vesicles prepared from rabbit kidney cortex were incubated at 37 degrees C for 30 min with phosphatidylinositol-specific phospholipase C. This maneuver resulted in a release of approx. 85% of the brush-border membrane-linked enzyme alkaline phosphatase as determined by its enzymatic activity. Transport of inorganic [32P]phosphate (100 microM) by the PI-specific phospholipase C-treated brush-border membrane vesicles was measured at 20-22 degrees C in the presence of an inwardly directed 100 mM Na+ gradient. Neither initial uptake rates, as estimated from 10-s uptake values (103.5 +/- 6.8%, n = 7 experiments), nor equilibrium uptake values, measured after 2 h (102 +/- 3.4%) were different from controls (100%). Control and PI-specific phospholipase C-treated brush-border membrane vesicles were extracted with chloroform/methanol to obtain a proteolipid fraction which has been shown to bind Pi with high affinity and specificity (Kessler, R.J., Vaughn, D.A. and Fanestil, D.D. (1982) J. Biol. Chem. 257, 14311-14317). Phosphate binding (at 10 microM Pi) by the extracted proteolipid was measured. No significant difference in binding was observed between the two types of preparations: 31.0 +/- 9.37 in controls and 29.8 +/- 8.3 nmol/mg protein in the proteolipid extracted from PI-specific phospholipase C-treated brush-border membrane vesicles. It appears therefore that alkaline phosphatase activity is essential neither for Pi transport by brush-border membrane vesicles nor for Pi binding by proteolipid extracted from brush-border membrane. These results dissociate alkaline phosphatase activity, but not brush-border membrane vesicle transport of phosphate, from phosphate binding by proteolipid.     

The effect of essential fatty acid deficiency on the stimulation of intestinal calcium transport by 1,25-dihydroxyvitamin D3

The effect of altering the lipid composition of the brush-border membrane on the ability of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) to stimulate calcium transport across the intestinal mucosa was examined by raising chicks on a vitamin D, essential fatty acid-deficient diet (-DEFAD) and measuring calcium absorption from duodenal sacs in situ and calcium uptake into brush-border membrane vesicles in vitro. Administration of 1,25-(OH)2D3 to -DEFAD and to -D control chicks led to the same increase in calcium transport in situ, whereas calcium transport in isolated brush-border membrane vesicles was not stimulated in the EFAD group, but responded normally in the control group. When the incubation temperature was increased to 34 degrees C, brush-border membrane vesicles from 1,25-(OH)2D3-treated essential fatty acid-deficient (+DE-FAD) chicks accumulated calcium at a faster rate than did vesicles from -DEFAD chicks. There was a marked decrease in the linoleic acid content and an increase in the oleic acid content of both the total lipid extract of the brush-border membrane as well as the phosphatidylcholine and phosphatidylethanolamine fractions, which could explain the temperature sensitivity of the in vitro system. When the diet of the EFAD chicks was supplemented with linoleic acid, the rate of calcium uptake into subsequently isolated vesicles from +DE-FAD chicks correlated with the amount of linoleic acid in the brush-border membranes. These results support the concept that the action of 1,25-(OH)2D3 on membrane lipid turnover and structure plays a critically important role in the 1,25-(OH)2D3-mediated cellular transport responses.     

Rapid flip-flop of oleic acid across the plasma membrane of adipocytes

Nonesterified long-chain fatty acids may enter cells by free diffusion or by membrane protein transporters. A requirement for proteins to transport fatty acids across the plasma membrane would imply low partitioning of fatty acids into the membrane lipids, and/or a slower rate of diffusion (flip-flop) through the lipid domains compared to the rates of intracellular metabolism of fatty acids. We used both vesicles of the plasma membrane of adipocytes and intact adipocytes to study transmembrane fluxes of externally added oleic acid at concentrations below its solubility limit at pH 7.4. Binding of oleic acid to the plasma membrane was determined by measuring the fluorescent fatty acid-binding protein ADIFAB added to the external medium. Changes in internal pH caused by flip-flop and metabolism were measured by trapping a fluorescent pH indicator in the cells. The metabolic end products of oleic acid were evaluated over the time interval required for the return of intracellular pH to its initial value. The primary findings were that (i) oleic acid rapidly binds with high avidity in the lipid domains of the plasma membrane with an apparent partition coefficient similar to that of protein-free phospholipid bilayers; (ii) oleic acid rapidly crosses the plasma membrane by the flip-flop mechanism (both events occur within 5 s); and (iii) the kinetics of esterification of oleic acid closely follow the time dependence of the recovery of intracellular pH. Any postulated transport mechanism for facilitating translocation of fatty acid across the plasma membrane of adipocytes, including a protein transporter, would have to compete with the highly effective flip-flop mechanism.     

Isolation of biochemical mutants using haploid mesophyll protosplasts of Hyoscyamus muticus

The question of whether membrane expansion, which is caused by anesthetics in animal systems, alters the lipid composition of plant cell membranes was investigated. We have measured the effects of several anesthetics on the relative amounts of the principal fatty acids from the polar lipids of barley (Hordeum vulgare L.) root membranes. Procaine, dibucaine, tetracaine, chloroform and, to a lesser degree, methanol increased the proportions of palmitic, stearic and oleic acids and decreased the proportions of linoleic and linolenic acids. Ethanol had no significant effect. Total amounts of the fatty acids from the polar lipids of roots in procaine solution decreased markedly so that all of the acids decreased in amount. The anesthetic was effective as soon as the roots were introduced to the solution and the changes progressed at constant rates for 6 h. Only the polar membrane lipids were altered; other lipids were not affected. Increased hydrostatic pressure of about 1.0 MPa largely prevented the anesthetic effects, including the decrease in the total amounts of the fatty acids. Hydrostatic pressure as high as 2 MPa had no effect per se on the membrane lipid composition. These results indicate that anesthetics cause expansion of the root membranes which results in the lipid changes. That a compositional change in the membrane lipids involves a conformational change such as expansion is an indication of the nature of the link between changes in the membrane lipids and changes in function of areas where hydrophilic ions permeate.Abbreviations 16:0 palmitic acid - 18:0 stearic acid - 18:1 oleic acid - 18:2 linoleic acid - 18:3 linolenic acid     

pH-sensitive transport of Fe2+ across purified brush-border membrane from mouse intestine

Recent studies of Fe2+ uptake by mouse proximal intestine brush-border membrane vesicles revealed low-affinity, NaCl-sensitive and high-affinity, NaCl-insensitive, components of uptake (Simpson, R.J. and Peters, T.J. (1985) Biochim. Biophys. Acta 814, 381-388). In this study, the former component is demonstrated to show a strong pH dependence with an optimum of pH 6.8-6.9. Studies at pH 6.5, where the low affinity component is inhibited by more than 25-fold compared with pH 7.2, suggest that the pH-sensitive component represents transport across the brush-border membrane followed by intravesicular binding. Cholate extracts of brush-border membrane vesicles contain pH- and NaCl-sensitive Fe2+ binding moieties which may be involved in the transfer of Fe2+ across the intestinal brush-border membrane and subsequent binding inside the vesicles. Fe2+ uptake by brush-border membrane vesicles from the duodenum of hypoxic mice is higher than uptake by vesicles from control-fed animals, suggesting the existence of a regulable brush-border membrane Fe2+ carrier.     

Lipid composition of squirrel monkey (Saimiri sciureus) saliva

The content and composition of lipids in saliva of healthy caries-free squirrel monkeys were investigated. The dialyzed and lyophilized saliva on extraction with chloroform/methanol yielded 8.0 +/- 0.9 mg of lipids/100 ml of saliva. Following fractionation on silicic acid column, 30.9% of lipids were found in the neutral lipid fraction, 58.8% in the glycolipid fraction, and 10.3% in the phospholipid fraction. The neutral lipids exhibited high content of free fatty acids (58.8%) and triglycerides (23.3%), the glycolipids consisted mainly of neutral and sulfated glyceroglucolipids (95%), while the phospholipids were rich in sphingomyelin and phosphatidylcholine. The results show that squirrel monkey saliva, while displaying lipid content similar to that of caries-susceptible humans, contains 50% less lipids than saliva of periodontal disease-prone marmoset.     

Studies on methanol-oxidizing yeast

The yeast strain 11Bh was studied from the aspect of qualitative and qunatitative composition of lipids formed in cells during growth on methanol, synthetic ethanol and glucose. The strain was found to form some 3% free fatty acids toward the end of the growth phase. More esterified fatty acids are formed on ethanol and glucose (2.75 and 2.86%, respectively) than on methanol (1.6%). The composition of lipids and representation of the various fatty acids in the lipids is similar on all three substrates. The cell lipids contain over 40 rel.% oleic and about 16 rel.% each of palmitoleic, palmitio and linolenic acid. Odd-numbered fatty acids are present after growth on any of the three substrates, amounting to at most 4 rel.%. Of the extracellular fatty acids formed toward the end of growth of cells on methanol, propionic and acetic acid occurred in largest amounts in the medium. An erratum to this article is available at .     

Brush border membrane non-esterified fatty acids. Physiological levels and significance for mucosal iron uptake in mouse proximal intestine

Brush border membrane vesicles prepared using divalent cation precipitation methods can contain unphysiological levels of non-esterified fatty acids. Fatty acid production from endogenous lipid during brush border membrane vesicle preparation is effectively prevented by the lipase inhibitor diethyl 4-nitrophenylphosphate plus cooling. Vesicles prepared using this procedure have variable levels of non-esterified fatty acids (range 22-193 nmol mg-1 protein). Changes in non-esterified fatty acid levels in brush border membrane vesicles parallel Fe uptake by vesicles from Fe/ascorbate solutions. Brush border membrane vesicle fatty acids appear to be derived from the diet but hypoxic mice are able to maintain high brush border membrane non-esterified fatty acid levels despite reduced dietary intake. Non-esterified fatty acids in brush border membrane may thus provide a physiological mechanism of mucosal Fe uptake.     

Effects of freezing and drying grass products prior to fatty acid extraction on grass fatty acid and lipid class composition--a technical note

Grass and grass silage represent a rich and natural source of omega-3 polyunsaturated fatty acids, in particular linolenic acid, for ruminants. Recent research, focusing on improving the content of these beneficial fatty acids in grass, requires storage of the forage samples prior to analysis. In this study, we evaluated whether conservation of fresh grass and grass silage by freezing (1 and 4 weeks,--18 degrees C) and/or drying (24h, 50 degrees C) affected its fatty acid content and induced shifts between lipid classes. FA were extracted using chloroform/methanol (2/1, v/v) and triacylglycerols (TAG), free fatty acids (FFA) and polar lipids (PL) were separated by thin layer chromatography. Fatty methyl esters (FAME) were identified by gas chromatography. Loss of thawing liquor might provoke a dramatic decrease in extractable lipid after frozen storage of both grass and grass silage. Morever, after frozen storage, fatty acids in grass but not in grass silage seem subjected to a higher rate o f lipolysis and oxidation, as suggested by increased quantities of FFA (3.1, 7.6, 8.4 % of total FAME) and reduced proportions of poly-unsaturated fatty acids (79.5, 73.6 and 74.1 % of total FAME) when analysing fresh grass samples directly or after 1 and 4 weeks of frozen storage, respectively. Drying of fresh grass did not provoke changes in FA composition, but distribution of FA over lipid classes was significantly altered, with an increase in TAG (5.1 to 17.9 % of total FAME) and FFA (2.4 to 14.9 % of total FAME) and lower proportions of PL (90.7 to 55.7 % of total FAME).     

Lipid content during sexual development in the homothallic mucor Zygorhynchus moelleri

In Zygorhynchus moelleri, a homothallic Mucor, triglycendes are the main components of chloroform/methanol extractable lipids. The triglycerides accumulate in the aerial hyphae, particularly in the developing zygospores and in the lateral suspensors, but only after zygospore maturation. They are probably transported from the submerged mycelium to the aerial hyphae. Most of the fatty acid synthetase activity is found in the submerged mycelium. The fatty acid composition of the triglycerides does not change appreciably during sexual development. No influence of trisporic acids has been found on triglyceride synthesis or transport.     

Unusual fatty acid composition of cerebrosides from the filamentous soil fungus Mortierella alpina

The cerebrosides produced by the soil filamentous fungus Mortierella alpina strain KG-1/95 account for about 13% of the total polar lipids extractable from lyophilised cells with chloroform/methanol mixtures. By means of 1H NMR and (13)C NMR spectroscopy, matrix-assisted laser-desorption ionisation mass spectrometry, and chemical degradation experiment, they have been shown to be 1-O-beta-D-glucopyranosyl-2-N-(2'-D-hydroxyalkanoyl)-9-methylsphinga-4(E),8(E)-dienines, the fatty acid composition of which is unusual and consists of 2-hydroxytridecanoic (4%), 2-hydroxytetradecanoic (60%), 2-hydroxypentadecanoic (20%), and 2-hydroxyhexadecanoic (16%) acids.     

Nonesterified fatty acids inhibit iron-dependent lipid peroxidation

The effect of various fatty acids on lipid peroxidation of liver microsomes induced by different methods in vitro was studied using oxygen uptake and malonaldehyde (MDA) production. It was observed that fatty acids with a single double bond are effective inhibitors of peroxidation. Stereo and positional isomers of oleic acid were equally effective as oleic acid. There was an absolute requirement for a free carboxyl group, since methyl esters of fatty acids and long-chain saturated and unsaturated hydrocarbons could not inhibit peroxidation. Saturated fatty acids with a chain length of 12-16 carbon atoms showed inhibition, whereas more than 18 carbon atoms reduced the inhibitory capacity. Fatty acids of lower chain length such as capric and caprylic acids did not show inhibition. Fatty acid inhibition was partially reversed by increasing the concentration of iron in the system. Peroxidation induced by methods which were independent of iron was not inhibited by fatty acids. It was observed that intestinal microsomes which were resistant to peroxidation due to the presence of nonesterified fatty acids in their membrane lipids were able to peroxidise by methods which do not require iron. These results suggest that certain fatty acids inhibit peroxidation by chelating available free iron. In addition, they may also be involved in competing with the esterified fatty acids in the membrane lipids which are the substrates for peroxidation.     

The lipid content of cell walls obtained from juvenile,yeast-like and filamentous cells ofCandida albicans

Purified cell walls ofCandida albicans obtained from juvenile cells, mature yeast-like cells and filamentous cells were analyzed for their lipid components. Chloroform: methanol (2:1 v v) extraction of the acetone-treated dried cell walls indicated the total lipid content to be 2.1% of the dry weight of the juvenile cell walls, 1.8% of the mature yeast-like cell walls and 4.5% of the filamentous cell walls. Separation of the chloroform: methanol extractable fraction through a silicie acid column and quantitative determination of the fractions showed significant amounts of sterol esters, triglycerides, sterols, free fatty acids, and phospholipids in these extracts. Following acetone extraction sterols were shown to constitute a greater percentage of the cell wall of juvenile cells than mature cells. Thin-layer chromatography separated the acetone-extractable lipids into at least four components. Diethyl ether extracts of the cell walls indicated the presence of small amounts of glycerol phospholipids in the cell walls of juvenile and mature yeast cells. Boiling 95% ethanol also removed a small lipid fraction from the cell walls of both juvenile and mature yeast which could include sphingosine phosphatides or glycosides.     

Relation between Ca2+ uptake and fluidity of brush-border membranes isolated from rabbit small intestine and incubated with fatty acids and methyl oleate

The rate of incorporation of oleic acid into isolated brush-border membranes was found to be considerably faster than methyl oleate incorporation under similar experimental conditions. The effects of fatty acids and methyl oleate incorporation on Ca2+ uptake and fluidity were monitored. Whereas treatment with 0.01-0.05 mM oleic acid corresponding to incorporations smaller than 90 nmol/mg protein enhanced Ca2+ transport, exposures to higher concentrations of this fatty acid corresponding to incorporations larger than 150 nmol/mg protein, decreased uptake of this cation. On the other hand, treatment with 0.01-0.2 mM methyl oleate corresponding to incorporations of up to 220 nmol/mg protein had only a stimulatory effect on the Ca2+ uptake. Oleic acid, linoleic acid and methyl oleate decreased the fluorescence anisotropy of membranes labelled with diphenylhexatriene in a dose-dependent manner. In contrast, palmitic acid had little or no effect on the diphenylhexatriene-reportable order of the membrane within the range of concentrations used. Monitored as a function of temperature, the anisotropy values showed a gradual melting for both the control and lipid-treated membranes. The results support the concept that saturated and cis-unsaturated fatty acids dissolve in different lipid domains and this in itself appears to be an important factor defining whether the biological function of the membrane is affected by the uptake. Incorporation of cis-unsaturated fatty acids in domains harboring the Ca2+ uptake process increases Ca2+ uptake in concert with increased diphenylhexatriene-monitored fluidity. However, when concentrations of such fatty acids in these domains become sufficiently great, the presence of a largely increased number of free carboxyl groups at the membrane surface causes inhibition of Ca2+ uptake.     

High rates of [1-14C]acetate incorporation into the lipid of isolated spinach chloroplasts.

Spinach chloroplasts, isolated by techniques yielding preparations with high O2- evolving activity, showed rates of light-dependent acetate incorporation into lipids 3-4 fold higher than any previously reported. Incorporation rates as high as 500 nmol of acetate/h per mg of chlorophyll were measured in buffered sorbitol solutions containing only NaHCO3 and [1-14C]acetate, and as high as 800 nmol/h per mg of chlorophyll when 0.13 mM-Triton X-100 was also included in the reaction media. The fatty acids synthesized were predominantly oleic (70-80% of the total fatty acid radioactivity) and palmitic (20-25%) with only minor amounts (1-5%) of linoleic acid. Linolenic acid synthesis was not detected in the system in vitro. Free fatty acids accounted for 70-90% of the radioactivity incorporated and the remainder was shared fairly evenly between 1,2-diacylglycerols and polar lipids. Oleic acid constituted 80-90% of the free fatty acids synthesized, but the diacylglycerols and polar lipids contained slightly more palmitic acid than oleic acid. Triton X-100 stimulated the synthesis of diacylglycerols 3-6 fold, but stimulated free fatty acid synthesis only 1-1.5-fold. Added glycerol 1-phosphate stimulated both the synthesis of diacylglycerols and palmitic acid relative to oleic acid, but did not increase acetate incorporation into total chloroplast lipids. CoA and ATP, when added separately, stimulated acetate incorporation into chloroplast lipids to variable extents and had no effect on the types of lipid synthesized, but when added together resulted in 34% of the incorporated acetate appearing in long-chain acyl-CoA. Pyruvate was a much less effective precursor of chloroplast fatty acids than was acetate.     

The distribution of oleic acid between chylomicron-like emulsions, phospholipid bilayers, and serum albumin. A model for fatty acid distribution between lipoproteins, membranes, and albumin

In the process of lipoprotein lipolysis, masses of fatty acid are generated at the surface of the lipoprotein. The newly generated fatty acid may at least partly redistribute from the site of lipolysis to phospholipid-rich membranes and to albumin. We have studied the distribution of [1-13C]oleic acid in model systems consisting of chylomicron-like triacylglycerol-rich emulsions, unilamellar phosphatidylcholine vesicles, and bovine serum albumin. By using high resolution 13C NMR spectroscopy it was possible to distinguish fatty acid in each compartment (emulsion, vesicle, albumin) and quantitate the fatty acid distribution under various conditions of lipid compartment concentration and aqueous pH. When emulsions and vesicles were present in equivalent mass amounts, fatty acid exhibited a profound preference for the lipid bilayers. The release of oleic acid to phospholipid bilayers was presumably also a function of its high molar stoichiometry (5:1) with the albumin present. More equitable distributions of fatty acid between vesicles and emulsions were seen when higher concentrations of emulsion were used. The distribution of fatty acid between compartments was in good agreement with predictions made using the apparent ionization constant, expressed as pKapp, of 7.5 and the surface to core (phospholipid to triacylglycerol) distribution coefficient of 7.0, measured for unionized oleic acid in chylomicron particles (Spooner, P. J. R., Bennett Clark, S., Gantz, D. L., Hamilton, J. A., and Small, D. M. (1988) J. Biol. Chem. 263, 1444-1455). These results indicate that the affinities of fatty acid for phospholipid bilayer and chylomicron-like emulsion surfaces are equivalent. Redistribution of lipolytically generated fatty acid from chylomicron surface to cell membrane may simply be driven by the predominant quantity of the cell membrane surfaces.     

Lipids and fatty acids in cellulosomes of Clostridium thermocellum

A lipid component was found in cellulosomes (multienzymatic cellulase complexes) of the thermophilic bacterium Clostridium thermocellum. Two major fractions of the cellulosomes have been studied, one with a relative molecular mass (M_r) of 10–50 million (polycellulosomes, fraction A) and the other with an M_r 0.5–10 million (fraction B) It was found that the larger cellulosomes contained higher relative amounts of lipids (8.1%) as well as Ca²⁺ ions (0.6%), and showed higher cellulolytic activity Among the lipids was cardiolipin, 1,2- and 1,3-diglycerides, triglycerides, and up to 11 free fatty acids, including both saturated (palmitic, lauric, myristic, pentadecanoic, stearic, arachinic) and unsaturated (myristoleic, palmitoleic, and oleic) moieies Cardiolipin was a major phospholipid component in cellulosomes and was also found to be a major phospholipid component of the cell membrane, palmitic acid was a major fatty acid Fraction B contained less fatty acids (0.5% vs 1.27% in fraction A) with fewer acids detected than in fraction A Removal of the extractable lipids led to fragmentation of the cellulosomes with a concurrent sharp drop in their enzymatic activity Total removal of the lipids from cellulosomes was possible only when the proteins were completely denatured The qualitative composition of the extractable and non-extractable fatty acids was the same The lipid component of the cellulosomes, containing a high content of the unsaturated fatty acids, was located mainly in the part of cellulosomes that is in tight contact with the cellulose surface, and it apparently plays an important role in the tight adsorption of the cellulosomes on cellulose.