The glycerol teichoic acid of walls of Staphylococcus lactis I3

1. The teichoic acid from walls of Staphylococcus lactis I3 was isolated by extraction with trichloroacetic acid and shown to contain glycerol, N-acetylglucosamine, phosphate and d-alanine in the molecular proportions 1:1:2:1. The alanine is attached to the polymer through ester linkages. 2. Hydrolysis with acid gave alanine, glucosamine and glycerol diphosphates. Under mild acid conditions a repeating unit was produced; this consists of glycerol diphosphate joined through a phosphodiester group to N-acetylglucosamine. 3. Hydrolysis with alkali gave glycerol diphosphates, saccharinic acid and two phosphodiesters containing glucosamine whose structures were elucidated; these both contain glucosamine 1-phosphate, and N-acetylglucosamine 1-phosphate was isolated by a degradative procedure. 4. The unusual properties of the teichoic acid are explained by a polymeric structure in which N-acetylglucosamine 1-phosphate is attached through its phosphate to glycerol phosphate. 5. The biosynthetic implications of this structure are discussed.     

The effect of two isomeric octadecenoic acids on the lipid metabolism and growth of Novikoff hepatoma cells.

The origin and metabolism of octadecenoic acid (18 : 1) was examined in intact Novikoff rat hepatoma cells by using labeled precursors and two isomeric octadecenoic acids which differed in their abilities to stimulate cell growth in a serum-free medium. The isomers (ci-6-18 : 1 and cis-9-18 : 1) were measured in the cellular lipid by ozonolysis and reduction of the ozonides. The results indicate that the 18 : 1 fatty acid accumulated in the cell lipid by uptake of the preformed acid from the medium. The cis-9-18 : 1 to 16 : 1 and 20 : 1 fatty acids by chain shortening and chain elongation. Both isomers inhibited de novo fatty acid synthesis from acetate by cells suspended in a serum-free medium. The isomers did not exert coordinate control of both fatty acid and cholesterol biosynthesis in the Novikoff cells.     

Activation of synthesis of hexacosenoic acid by sulfhydryl reagents in swine cerebral microsomes

The elongation of icosenoyl-CoA (20:1-CoA) in swine cerebral microsomes resulted in the synthesis of docosenoic acid (22:1) and tetracosenoic acid (24:1), but the synthesis of hexacosenoic acid (26:1) was negligible. In contrast, in the presence of sulfhydryl reagents (0.6 mM N-ethylmaleimide [NEM] or 0.3 mM p-chloromercuriphenylsulfonic acid [PCMPS]) the synthesis of 26:1 was remarkably enhanced. We suggest that the synthesis of 26:1 from 20:1-CoA was more enhanced by NEM or PCMPS as a result of activation of the condensation step in the elongation of 24:1 (intermediate) to 26:1.     

Amino acid sequence of the threonine-containing mureins of coryneform bacteria

In a study of the mureins of coryneform bacteria (Arthrobacter, Brevibacterium, Cellulomonas, Corynebacterium, Erysipelothrix), 21 threonine-containing strains were found. In several of the strains the amino acid and amino sugar composition of the murein was muramic acid (Mur), glucosamine (GlcNH(2)), d-Glu, l-Lys, l-Thr, and Ala in a molar ratio of 1:1:1:1:1:4 or 5, and in several other strains it was Mur, GlcNH(2), d-Glu, l-Lys, l-Thr, Ala, and l-Ser in a molar ratio of 1:1:1:1:1:3:1. The amino acid sequence of the mureins was determined by analyzing the oligopeptides derived from partial acid hydrolysates. It was shown that there were five different murein types. The peptide subunits attached to the muramic acid are the same, namely l-Ala-d-GluNH(2)-l-Lys-d-Ala. In one strain, the alpha-carboxyl group of d-Glu is substituted by d-alanine amide. The interpeptide bridges of the different types consist of the peptides l-Ala-l-Thr-l-Ala, l-Ala-l-Thr, l-Ala-l-Ala-l-Thr, l-Ala-l-Ala-l-Ala-l-Thr, or l-Ala-l-Thr-l-Ser which are bound through their C-termini (l-Ala, l-Thr, l-Ser) to the epsilon-amino group of l-Lys of one peptide subunit and by their N-termini (l-Ala) to the C-terminal d-Ala of an adjacent peptide subunit. Determination of the N- and C-terminal groups in the mureins showed that about 15 to 30% of the interpeptide bridges are not cross-linked.     

Fatty acids of pulmonary surfactant phosphatidylcholine from fetal rabbit lung tissue in culture. Biosynthesis of n-10 monoenoic fatty acids

We have previously reported that fetal rabbit lung tissue in organ culture produces a lamellar body material (pulmonary surfactant) with a lower percentage of disaturated phosphatidylcholine than is typically found in rabbit lung in vivo (Longmuir, K.J., C. Resele-Tiden, and L. Sykes. 1985. Biochim. Biophys. Acta. 833: 135-143). This investigation was conducted to identify all fatty acids present in the lamellar body phosphatidylcholine, and to determine whether the low level of disaturated phosphatidylcholine is due to excessive unsaturated fatty acid at position sn-1, sn-2, or both. Fetal rabbit lung tissue, 23 days gestation, was maintained in culture for 7 days in defined (serum-free) medium. Phospholipids were labeled in culture with [1-14C]acetate or [U-14C]glycerol (to follow de novo fatty acid biosynthesis), or with [1-14C]palmitic acid (to follow incorporation of exogenously supplied fatty acid). Radiolabeled fatty acid methyl esters obtained from lamellar body phosphatidylcholine were first separated by reverse-phase thin-layer chromatography (TLC) into two fractions of 1) 14:0 + 16:1 and 2) 16:0 + 18:1. Complete separation of the individual saturated and monoenoic fatty acids was achieved by silver nitrate TLC of the two fractions. Monoenoic fatty acid double bond position was determined by permanganate-periodate oxidation followed by HPLC of the carboxylic acid phenacyl esters. Lamellar body phosphatidylcholine contained four monoenoic fatty acids: 1) palmitoleic acid, 16:1 cis-9; 2) oleic acid, 18:1 cis-9; 3) cis-vaccenic acid, 18:1 cis-11; and 4) 6-hexadecenoic acid, 16:1 cis-6. In addition, 8-octadecenoic acid, 18:1 cis-8, was found in the fatty acids of the tissue homogenate. The abnormally low disaturated phosphatidylcholine content in lamellar body material was the result of abnormally high levels of monoenoic fatty acid (principally 16:1 cis-9) found at position sn-2. Position sn-1 contained normal levels of saturated fatty acid. The biosynthesis of the unusual n-10 fatty acids was observed from the start of culture throughout the entire 7-day culture period, and was observed in incubations of tissue slices of day 23 fetal rabbit lung. This is the first report of the biosynthesis of n-10 fatty acids (16:1 cis-6 and 18:1 cis-8) in a mammalian tissue other than skin, where these fatty acids are found in the secretory product (sebum) of sebaceous glands.     

Development of an attractant for the scarab pest Macrodactylus subspinosus (Coleoptera: Scarabaeidae)

Field trials were conducted over several seasons to determine the attractant most successful in luring adult rose chafers, Macrodactylus subspinosus (F.), to traps. During the first season, 20 compounds were compared with the standard lure, valeric acid + hexanoic acid + octyl butyrate (1:1:1). The two new standards establishedthat season were: valeric acid + 1-nonanol (1:1); and valeric acid + hexanoic acid + octyl butyrate + 1-nonanol (1:1:1:1). The following season, 36 compounds were evaluated, comparing them to the new standards. The performance of the standard binary lure valeric acid + 1-nonanol was improved when the alcohol 1-nonanol was replaced by its analog trans-2-nonenol and this was confirmed during the third season. At the same time, a second test was conducted with 29 new candidates, which were combined with valeric acid and compared with the standard: valeric acid + hexanoic acid + octyl butyrate + 1-nonanol (1:1:1:1). A control and the single compound alpha-ionone were included, resulting in the discovery of a new more powerful attractant, alpha-ionone. Testing of alpha-ionone continued the following season, at which time the initial leading candidate and new ones containing trans-2-nonenol were tested against the single attractant alpha-ionone and various combinations of it. A new five-component mixture of valeric acid, hexanoic acid, octyl butyrate, trans-2-nonenol, and alpha-ionone out performed all other lure combinations.     

Occurrence of ribitol-containing lipoteichoic acid in Staphylococcus aureus H and its glycosylation

A ribitol-containing lipoteichoic acid was obtained from the 20,000 x g supernatant fraction of Staphylococcus aureus H by extraction with Triton X-100 followed by fractionation on Sepharose 6B and DEAE-cellulose columns. The purified lipoteichoic acid was composed of phosphate, glycerol, glucose, glucosamine, ribitol, and fatty acids in a molar ratio of 1 : 0.9 : 0.06 : 0.03 : 0.09 : 0.07. Based on the structural analysis of fragments from alkali and HF hydrolysis, the lipoteichoic acid appears to consist of three moieties, namely a ribitol phosphate oligomer, poly(glycerol phosphate) which has about 30 glycerol phosphate units, and beta-glucosyl-beta-glucosyl(1 leads to 1)diacylglycerol. N-Acetylglucosamine was linked to the ribitol residues. The lipoteichoic acid serves as an acceptor of glycosyl moieties from UDP-glucose and UDP-N-acetylglucosamine in the enzyme reaction catalyzed by the membrane preparation. The rate of enzymatic glycosylation was increased by prior treatment of the lipoteichoic acid with N-acetyl-beta-D-glucosaminidase. The glycosylation seems to occur at the ribitol residues of the lipoteichoic acid.     

Morphology and Chemistry of the Bacterial Cell Wall

The location of the mucopeptide in the cell wall of Bacteroides convexus was determined by electron microscope after enzymatic and chemical treatment (papain, pepsin, lysozyme and phenol). In the five layered cell wall the innermost electron dense layer (or a part of it) proved to be the mucopeptide. The molar ratio of amino sugar and amino acid components of purified mucopeptide was about 1:1:1:1:1:1 for glucosamine, muramic acid, L-alanine, D-glutamic acid, DL(meso)-diaminopimelic acid and D-alanine.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

A monoclonal antibody recognizing the chlorohydrin derivatives of oleic acid for probing hypochlorous acid involvement in tissue injury

Summary

A monoclonal antibody against hypochlorous acid—modified oleic acid has been raised to investigate involvement of HOCI in tissue injury. Mice were immunized with an isomeric mixture of chlorohydrin derivatives of oleic acid (18:0-chlorohydrin) conjugated to keyhole limpet haemocyanin (CH-KLH). The chlorohydrin was formed by the treatment of oleic acid with hypochlorous acid. Monoclonal antibodies were raised and the fusion was screened with 18:0-chlorohydrin-bovine serum albumin (CH-BSA) conjugate. A number of antibody-secreting clones were identified and the supernatants were characterized by binding studies and dose-response curves. In ELISA, mAb CH-1 had an equivalent titre when either the chlorohydrin or bromohydrin derivative of oleic acid, complexed to bovine serum albumin, was used as screening antigen. The mAb CH-1 recognition of CH-BSA was competed with chlorohydrin and bromohydrin conjugates of BSA and KLH. Similarly, free 18:0-chlorohydrin and the 18:0-chlorohydrin-phosphatidyl choline treated with hypochlorous acid competed with mAb CH-1 binding. The mAb CH-1 also recognised the chlorohydrin derivative of linoleic acid and chlorohydrin formed from palmitoyl, oleyl phosphatidyl choline but with a decreased avidity. Weak cross-reactivity was observed with hydroxy-linoleic acid and linoleic acid hdroperoxide, either as free fatty acid or in phosphatidyl choline. There was minimal competitive binding of mAb CH-1 to free oleic acid, 16:0/18:1 phosphatidylcholine, cholesterol, or cholesterol chlorohydrin.

The mAb CH-1 described here may be a useful probe for assessing the involvement of hypochlorous acid in tissue injury.     

Structural elucidation of the EPS of slime producing Brevundimonas vesicularis sp. isolated from a paper machine

The slime forming bacteria Brevundimonas vesicularis sp. was isolated from a paper mill and its EPS was produced on laboratory scale. After production, the exopolysaccharide (EPS) was purified and analysed for its purity and homogeneity, HPSEC revealed one distinct population with a molecular mass of more than 2,000 kDa. The protein content was around 9 w/w%. The sample was analysed to determine its chemical structure. The EPS was found to consist of rhamnose, glucose, galacturonic acid and glucuronic acid. Due to the presence of uronic acids the molar ratio between the four sugars found varies from 3:5:2:4 by sugar composition analyses after methanolysis to 1:1:1:1 found by NMR. A repeating unit with a molecular mass of 678 Da was confirmed by MALDI-TOF mass spectrometry after mild acid treatment. 13C and 1H hetero- and homonuclear 2D NMR spectroscopy of the native and partial hydrolysed EPS revealed a repeating unit, no non-sugar substituents were present.     

Synthesis, 13C-NMR and CD study of the N-terminal tridecapeptide sequence of human fibroblast interferon

The N-terminal sequence H-Met-Ser-Tyr-Asn-Leu-Leu-Gly-Phe-Leu-Gln-Arg-Ser-Ser-OH (FIF[1-13]) of human fibroblast interferon HuIFN-beta(Fi) has been synthesized using the solid-phase method. After esterification of N-tert-butyloxycarbonyl-O-benzyl-L-serine cesium salt with chloromethylated polystyrene-1% divinylbenzene (loading 0.25 mmol/g) the tridecapeptide was built up stepwise. Coupling reagents and N-tert-butyloxycarbonylamino acids were used in a six-fold excess. For the second coupling 1-hydroxybenzotriazole was added during carbodiimide and 4-nitrophenyl glutaminate or asparaginate couplings. Side chain functions were masked: O-benzylserine, O-(2,6-dichlorobenzyl)tyrosine and Ng-tosylarginine. After an acetylation step the N-protection was removed by trifluoroacetic acid/dichloromethane 1:1, and for neutralisation triethylamine/-chloroform 1:9 were used, both steps with a prewash. The Ng-tosyltridecapeptide was split-off from the resin by HBr in trifluoroacetic acid and purified by repetitive precipitations. After deprotection of the guanidino group of arginine with sodium in liquid ammonia, the peptide was precipitated from acetic acid/water, chromatographed on Sephadex G-25 coarse in acetic acid/water 1:1 and precipitated from acetic acid/ether and dimethylformamide/acetone. After purification by multiplicative counter-current distribution in butanol/-5% acetic acid/propanol 5:5:1 the tridecapeptide was pure according to chromatographic, electrophoretic, enzymatic and instrumental analyses. The peptide was investigated by circular dichroism in trifluoroethanol and hexafluoroacetonesesquihydrate and 13C-nuclear magnetic resonance, which revealed an alpha-helical conformation. In order to obtain a suitable antigen the tridecapeptide was coupled to poly(L-lysine) (molecular mass 37300) via N,N'-dicyclohexylcarbodiimide followed by dialysis. The resulting poly(L-lysine)-FIF[1-13] conjugate showed a loading of 17.8 mol FIF[1-13] per mol poly(L-lysine).     

Structural study of phosphomannan-protein complex of Citeromyces matritensis containing beta-1,2 linkage. Application of partial acid degradation and acetolysis techniques under mild conditions

The phosphomannan-protein complex of Citeromyces matritensis IFO 0651 strain was investigated for its chemical structure by a sequential degradation procedure, partial acid degradation followed by acetolysis under mild conditions. Upon treatment with 10 mM HCl at 100 degrees C for 1 h, this complex released mannotriose and mannotetraose consisting solely of 1,2-linked beta-D-mannopyranosyl residues, ca. 20% on weight basis of the parent complex. The acid-degraded complex was then subjected to acetolysis using an acetolysis medium of low sulfuric acid concentration, a 100:100:1 (v/v) mixture of acetic anhydride, acetic acid, and sulfuric acid at 40 degrees C for 36 h. A phosphate-containing manno-oligosaccharide fraction eluted in the void-volume region of a Bio-Gel P-2 column was found to consist of Manp beta 1----2Manp beta 1----2Manp alpha 1----2Man to which 1 mol of phosphate group was attached, while a manno-oligosaccharide fraction eluted in the diffusable region was a mixture of Manp beta 1----2Manp beta 1----2Manp beta 1----2Manp alpha 1----2Man, Manp beta 1----2Manp beta 1----2Manp alpha 1----2Man, Manp beta 1----2Manp alpha 1----2Man, Manp alpha 1----2Man, and mannose in the molar ratio of 0.08:0.33:0.19:0.32:1.00. Therefore, the structural analysis of the polysaccharide moiety of a beta-1,2 linkage-containing phosphomannan-protein complex of fungal origin can be achieved by means of a sequential degradation procedure, partial acid degradation followed by acetolysis under mild conditions.     

The mechanism of action of the monoamine oxidase inhibitor pargyline

Purified pig liver monoamine oxidase, which has been shown to contain one mole of covalently bound FAD per mole of enzyme, was inhibited by [¹⁴C] Pargyline (N-methyl-N-2-(propynyl)-benzylamine) and then extensively degraded by pronase. The Pargyline-containing fragment was purified by gel filtration and ion-exchange chromatography. The equimolar ratio between Pargyline and flavin was retained after the purification. Thin-layer chromatography in several systems showed that Pargyline was bound to the flavo-peptide. Amino acid analyses of the peptide yielded cysteic acid, aspartic acid, serine and glycine in a molar ratio of 1:1:1:2.     

Structure of acidic polysaccharide from cell wall of Propionibacterium acnes strain C7

The structure of polysaccharide prepared by lysozyme digestion from the cell wall of Propionibacterium acnes strain C7 was examined. The polysaccharide fraction was composed of glucose, galactose, mannose, galactosamine, and diaminomannuronic acid in a molar ratio of 1:1:0.3:1:2. By Smith degradation of the polysaccharide, diaminouronic acid-containing fractions were obtained, and the configuration of diaminouronic acid was identified as 2,3-diacetamido-2,3-dideoxymannuronic acid [Man(NAc)2A] by means of 1H-NMR and 13C-NMR spectroscopic analyses. The results of analyses involving methylation and partial acid hydrolysis led to the conclusion that the polysaccharide has the repeating unit----6)Gal(alpha 1----4)Man(NAc)2A(beta 1----6)Glc(alpha 1----4)Man(NAc)2A (beta 1----3)GalNAc(beta 1--. In addition, a portion of the galactose residues were substituted at C-4 by alpha 1----2 linked mannotriose.     

Evidence for peroxisomal retroconversion of adrenic acid (22:4(n-6)) and docosahexaenoic acids (22:6(n-3)) in isolated liver cells

The intracellular localization of the oxidation of [2-14C]adrenic acid (22:4(n-6)) and [1-14C]docosahexaenoic acid (22:6(n-3)) was studied in isolated liver cells. The oxidation of 22:4(n-6) was 2-3-times more rapid than the oxidation of 22:6(n-3), [1-14C]arachidonic acid (20:4(n-6)) or [1-14C]oleic acid (18:1). (+)-Decanoylcarnitine and lactate, both known to inhibit mitochondrial beta-oxidation, reduced the oxidation of 18:1 distinctly more efficiently than with 22:4(n-6) and 22:6(n-3). In liver cells from rats fed a diet containing partially hydrogenated fish oil, the oxidation of 22:6(n-6) and 22:6(n-3) was increased by 30-40% compared with cells from rats fed a standard pellet diet. With 18:1 as substrate, the amount of fatty acid oxidized was very similar in cells from animals fed standard pellets or partially hydrogenated fish oil. Shortened fatty acids were not produced from [5,6,8,9,11,12,14,15-3H]arachidonic acid. In hepatocytes from rats starved and refed 20% fructose, a large fraction of 14C from 22:4 was recovered in 14C-labelled C14-C18 fatty acids. Oxidation of 22:4 thus caused a high specific activity of the extramitochondrial pool of acetyl-CoA. The results suggest that 22:4(n-6) and to some extent 22:6(n-3) are oxidized by peroxisomal beta-oxidation and by this are retroconverted to arachidonic acid and eicosapentaenoic acid.     

Biotransformation of 1-naphthalenesulfonic acid by the green alga Scenedesmus obliquus

Under sulfate limitation, axenic batch cultures of the green alga Scenedesmus obliquus metabolized 1-naphthalenesulfonic acid and partially used the sulfonate as a source of sulfur. The main metabolite, 1-hydroxy-2-naphthalenesulfonic acid, which was not metabolized further in the algal culture, was formed by hydroxylation of the substrate in position 1 and by migration of the sulfonic acid group to position 2 of the naphthalene ring (NIH shift). A smaller amount of 1-naphthalenesulfonic acid was desulfonated. The resulting 1-naphthol was mostly transformed into 1-naphthyl β-d-glucopyranoside. Received: 27 March 1996 / Revision received: 18 October 1996 / Accepted: 30 October 1996     

Dicer1 敲除对肝脏胆酸代谢和转运功能的影响

目的:微小RNA(microRNAs,miRNAs)在胆固醇的合成,代谢和转运中起着重要作用,而mi RNAs在胆固醇代谢物胆酸的代谢和转运中的作用尚不清楚。Dicer基因是miRNAs生成过程的关键酶。本课题使用肝脏特异的Dicer1基因敲除小鼠,考察肝脏Dicer1基因敲除对C57BL/6小鼠肝脏胆酸代谢和转运的影响。方法:使用白蛋白启动子驱动的Cre重组酶和Loxp系统(Alb-Cre/Loxp)在小鼠肝脏中特异的敲除Dicer1基因;分别收集3~12周龄的小鼠血液和肝脏组织,使用Cobas生化仪检测小鼠血液和肝脏中总胆酸含量;利用实时定量PCR的方法分析肝脏中胆汁酸代谢转运相关基因的表达。结果:实验发现,肝脏Dicer基因敲除后,胆酸在血液和肝脏中明显蓄积,弥漫性肝细胞轻微空泡化,偶见单个肝细胞坏死。检测胆酸代谢和转运相关基因的表达发现,胆酸合成相关基因的表达有轻度升高,但缺乏统计学差异;在肝脏细胞血管侧的胆酸摄取转运体中,Oatp1a1在Dicer1敲除小鼠肝脏中明显下调,Ntcp和Oatp1b2则无明显改变;而肝细胞血管侧胆酸外排转运体的表达均有显著升高,胆管侧的外排转运体中Abcb11表达有明显增加。结论:Dicer基因敲除后,胆酸在血液和肝脏中明显蓄积,肝脏和血液中胆酸总量显著增加。血液中胆酸的蓄积可能与肝脏细胞血管侧摄取转运体的低表达和血管侧外排转运体的高表达有关;而肝脏中胆酸的蓄积可能部分来自于轻度升高的胆酸合成酶,胆酸在肝细胞内运输途径的紊乱可能与肝脏和血液中胆酸总量的显著增加相关。     

Modification by clofibric acid of acyl composition of glycerolipids in rat liver. Possible involvement of fatty acid chain elongation and desaturation

Administration of p-chlorophenoxyisobutyric acid (clofibric acid) to rats induced a marked change in acyl composition of hepatic glycerolipids; a considerable increase in the proportion of octadecenoic acid (18:1) was accompanied by a marked decrease in the proportion of octadecadienoic acid (18:2). Among the glycerolipids, the changes in the proportions of 18:1 and 18:2 were the most marked in phosphatidylcholine. The change in the acyl composition of phosphatidylcholine paralleled the change in free fatty acid composition in microsomes. The treatment of rats with clofibric acid resulted in a 2.3-fold increase in activity of microsomal palmitoyl-CoA chain elongation and a 4.8-fold increase in activity of stearoyl-CoA desaturation. The activities of acyl-CoA synthetase, 1-acylglycerophosphate acyltransferase and 1-acylglycerophosphorylcholine acyltransferase in hepatic microsomes were increased approx. 3-, 1.7- and 3.6-times, respectively, by the treatment of rats with clofibric acid. These findings are discussed with respect to the role of fatty acid modification systems in the regulation of acyl composition of phosphatidylcholine.