Chemical characterization and physical and biological activities of rhamnolipids produced by Pseudomonas aeruginosa BN10

Pseudomonas aeruginosa BN10 isolated from hydrocarbon-polluted soil was found to produce rhamnolipids when cultivated on 2% glycerol, glucose, n-hexadecane, and n-alkanes. The rhamnolipids were partially purified on silica gel columns and their chemical structures elucidated by combination of one- and two-dimensional 1H and 13C NMR techniques and ESI-MS analysis. Eight structural rhamnolipid homologues were identified: Rha-C10-C8, Rha-C10-C10, Rha-C10-C12:1, Rha-C10-C12, Rha2-C10-C8, Rha2-C10-C10, Rha2-C10-C12:1, and Rha2-C10-C12. The chemical composition of the rhamnolipid mixtures produced on different carbon sources did not vary with the type of carbon source used. The rhamnolipid mixture produced by Pseudomonas aeruginosa BN10 on glycerol reduced the surface tension of pure water from 72 to 29 mN m(-1) at a critical micellar concentration of 40 mg 1(-1), and the interfacial tension was 0.9 mN m(-1). The new surfactant product formed stable emulsions with hydrocarbons and showed high antimicrobial activity against Gram-positive bacteria. The present study shows that the new strain Pseudomonas aeruginosa BN10 demonstrates enhanced production of the di-rhamnolipid Rha2-C10-C10 on all carbon sources used. Due to its excellent surface and good antimicrobial activities the rhamnolipid homologue mixture from Pseudomonas aeruginosa BN10 can be exploited for use in bioremediation, petroleum and pharmaceutical industries.     

Physicochemical characterization and antimicrobial properties of rhamnolipids produced by Pseudomonas aeruginosa 47T2 NCBIM 40044

Pseudomonas aeruginosa 47T2, grown in submerged culture with waste frying oil as a carbon source, produced a mixture of rhamnolipids with surface activity. Up to 11 rhamnolipid homologs (Rha-Rha-C(8)-C(10); Rha-C(10)-C(8)/Rha-C(8)-C(10);Rha-Rha-C(8)-C(12:1); Rha-Rha-C(10)-C(10); Rha-Rha-C(10)-C(12:1); Rha-C(10)-C(10); Rha-Rha-C(10)-C(12)/Rha-Rha-C(12)-C(10); Rha-C(10)-C(12:1)/Rha-C(12:1)-C(10); Rha-Rha-C(12:1)-C(12); Rha-Rha-C(10)-C(14:1); Rha-C(10)-C(12)/Rha-C(12)-C(10)) were isolated from cultures of P. aeruginosa 47T2 from waste frying oil and identified by HPLC-MS analysis. This article deals with the production, isolation, and chemical characterization of the rhamnolipid mixture RL(47T2). The physicochemical and biological properties of RL(47T2) as a new product were also studied. Its surface tension decreased to 32.8 mN/m; and the interfacial tension against kerosene to 1 mN/m. The critical micellar concentration for RL(47T2) was 108.8 mg/mL. The product showed excellent antimicrobial properties. Antimicrobial activity was evaluated according to the minimum inhibitory concentration (MIC), the lowest concentration of an antimicrobial agent that inhibits development of visible microbial growth. Low MIC values were found for bacteria Serratia marcescens (4 microg/mL), Enterobacter aerogenes (8 microg/mL), Klebsiella pneumoniae (0.5 microg/mL), Staphylococcus aureus and Staphylococcus epidermidis (32 microg/mL), Bacillus subtilis (16 microg/mL), and phytopathogenic fungal species: Chaetonium globosum (64 microg/mL), Penicillium funiculosum (16 microg/mL), Gliocadium virens (32 microg/mL) and Fusarium solani (75 microg/mL).     

Structural characterization of rhamnolipid produced by Pseudonomas aeruginosa strain FIN2 isolated from oil reservoir water

Biosurfactant-producing microorganisms inhabiting oil reservoirs are of great potential in industrial applications. Yet, till now, the knowledge about the structure and physicochemical property of their metabolites are still limited. The aim of this study was to purify and structurally characterize the biosurfactant from Pseudomonas aeruginosa strain FIN2, a newly isolated strain from an oil reservoir. The purification was conducted by silica gel column chromatography followed by pre-RP HPLC and the structural characterization was carried out by GC–MS combined with MS/MS. The results show that the biosurfactant produced by FIN2 is rhamnolipid in nature and its four main fractions were identified to be Rha-C10-C10(46.1 %), Rha–Rha-C10-C10(20.1 %), Rha-C8-C10 (7.5 %) and Rha-C10-C12:1(5.5 %), respectively. Meanwhile, the rarely reported rhamnolipid congeners containing β-hydroxy fatty acids of C6, C9, C10:1 and C11 were also proved to be present in the rhamnolipid mixture produced. The rhamnolipid mixture exhibited a strong surface activity by lowering the surface tension of distilled water to 28.6 mN/m with a CMC value of 195 mg/l.     

预水解发酵碳源对铜绿假单胞菌NY3产鼠李糖脂特性及应用效能的影响研究

发酵碳源对铜绿假单胞菌NY3(Pseudomonas aeruginosa NY3)产鼠李糖脂(Rhamnolipids,Rha)的特性影响较大。研究了利用废弃动物油作为发酵碳源时,其碱预水解和酶预水解对NY3菌发酵产鼠李糖脂产量、产物结构和性能的影响,从碳源水解酸值与水解产物、鼠李糖脂组分结构和实际应用效果进行了研究。碱、酶预水解实验发现,碳源酸值由初始的19.81 mg/g分别提高到72.04 mg/g和73.75 mg/g,气质联用(GC-MS)分析检测结果表明,碱、酶预水解后,碳源均释放7种C14-C18碳链的脂肪酸,鼠李糖脂产量由未预水解的8.28 g/L分别提高到15.35 g/L和17.63 g/L。液质联用(LCMS-IT-TOF)分析结果表明,用未预水解及碱、酶预水解碳源发酵时,NY3菌所产鼠李糖脂中单糖脂含量分别为62.07%、65.67%、87.32%。利用NY3菌在中试条件下处理高浓度石化企业油污泥,发现鼠李糖脂能促进NY3菌去除油污泥中的石油烃,且促进作用强弱顺序为未预水解产Rha碱预水解产Rha酶预水解产Rha。     

Very long-chain phenylpropyl and phenylbutyl esters from Taxus baccata needle cuticular waxes

The cuticular wax of Taxus baccata L. needles was found to contain four different classes of long-chain esters that were identified by various chemical transformations with product assignment employing GC-MS. Homologous series of (1) 3-(4'-hydroxyphenyl)-propyl esters of C(20)-C(36) fatty acids, (2) 4-(4'-hydroxyphenyl)-2-butyl esters of C(18)-C(28) fatty acids, (3) 3-(3',4'-dihydroxyphenyl)-propyl esters of C(20)-C(32) fatty acids, and (4) 4-(3',4'-dihydroxyphenyl)-2-butyl esters of C(18)-C(28) fatty acids were identified. The four compound classes amounted to 0.1-3.6 micro g/cm(2) of needle surface area, corresponding to 0.2-7.6% of the wax mixture, respectively. While both phenylpropyl ester series had a maximum for the homolog containing tetracosanoic acid, in the phenylbutyl esters homologs containing eicosanoic and docosanoic acids predominated.     

Identification of unusual fatty acids of four alpine plant species from the Pamirs

Fatty acid composition and structure in total lipids from the green above-ground parts of four alpine plants, Oxygraphis glacialis, Primula macrophylla, Rhodiola pamiroalaica, and Swertia marginata, were established by GC and GC-MS. A total of 55 fatty acids was detected, and 48 of them were identified. Ubiquitous palmitate, linoleate, and linolenate predominated in the lipids accounting for about 72-90% of the total fatty acids. At the same time, the latter contained numerous species, which were unusual for higher plants and included saturated odd-numbered n-acids (six C15-C25 species, 0.26-1.40%), saturated even-numbered very-long-chain n-acids (six C20-C30 species, 1.00-2.49%), iso-acids (nine C15-C26 species, 0.64-1.53%), anteiso-acids (four C15-C20 species, 0.08-1.57%), certain uncommon mono- and dienoic acids, as well as 16:3omega3, 18:3omega6, and 18:4omega3 acids that are absent from the most higher plants. Nine fatty acids were found here for the first time in higher plants and two may be new to science. The evidence on the unusual fatty acids is discussed with respect to their distribution in living organisms, pathways of biosynthesis, and chemotaxonomic role.     

Metabolic origins of urinary unsaturated dicarboxylic acids

Previously, we [Jin, S.-J., & Tserng, K.-Y. (1989) J. Lipid Res. 30, 1611-1619] reported the structures of urinary octenedioic acids occurring in patients with dicarboxylic aciduria. We proposed that these unsaturated octenedioic acids were derived from the oxidation of oleic and linoleic acids. By comparison with synthetic decenedioic acids, we have further identified the higher homologues of unsaturated dicarboxylic acids in urine as cis-5-decenedioic (c5DC10), cis-4-decenedioic (c4DC10), cis-3-decenedioic (cDC10), trans-4-decenedioic, trans-3-decenedioic, cis-5-dodecenedioic (c5DC12), cis-3-dodecenedioic (c3DC12), and trans-3-dodecenedioic acids. The presence of these isomeric decenedioic and dodecenedioic acids in urine is consistent with the proposed metabolic origins. In vitro studies using synthetic unsaturated fatty acids and rat liver homogenates support the proposed metabolic origins of these acids. The following metabolic sequences are proposed for metabolites derived from oleic acid: (route A) cis-5-tetradecenoic acid----cis-5-tetradecenedioic acid----c5DC12----c5DC10----suberic (DC8)----adipic (DC6); (route B) cis-3-dodecenoic acid----c3DC12----c3DC10----c3DC8 (cis-3-octenedioic)----DC6. A similar route is derived from linoleic acid: cis-4-decenoic acid----c4DC10----c4DC8 (cis-4-octenedioic)----DC6. The presence of a double bond at position 3, 4, or 5 of fatty acid appears to be rate limiting for further beta-oxidation; therefore, metabolic products with cis-3, cis-4, or cis-5 structure accumulate. Urinary DC8 and DC6 are derived partially from the metabolic degradation of these unsaturated dicarboxylic acids.     

Methoxylated fatty acids in Blumeria graminis conidia

The total fatty acids (FA) composition of Blumeria graminis f.sp. tritici conidia, the causal agent of wheat powdery mildew, was analyzed as a function of their age. A total of 19 FA (C12-C24 saturated and unsaturated) and unusual methoxylated fatty acids (mFA) were detected in young, intermediate and old conidia. Two very long chain methoxylated FA were identified by GC-MS as 3-methoxydocosanoic and 3-methoxytetracosanoic acids. Medium chain FA were predominant in young conidia (75%, including 13% of mFA) while very long chain fatty acids constituted the major compounds in old conidia (74%, including 30% of mFA). We have shown for the first time that the total FA composition is strongly correlated with the age of B. graminis f.sp. tritici (Bgt) conidia.     

电喷雾质谱法检测假单胞菌BS-03产鼠李糖脂及其自由酸前体(英文)

采用电喷雾质谱法可同时检测到假单胞菌BS-03发酵液提取物中的鼠李糖脂及其自由酸前体(3-羟基葵酸单体和二聚体)。根据ESI-MS/MS的双鼠李糖脂二级质谱图显示存在强度较高的m/z为205、247的特征碎片离子峰,而单鼠李糖脂中却不存在此特征碎片离子。同时自由酸前体的主要组分为C8,C10,C8C10/C10C8,C10C10。其同分异构体与鼠李糖脂同分异构体类似,其中短链位于羟基端的组分含量高于长链在羟基端的组分。     

Parvibaculum lavamentivorans DS-1T degrades centrally substituted congeners of commercial linear alkylbenzenesulfonate to sulfophenyl carboxylates and sulfophenyl dicarboxylates

Commercial linear alkylbenzenesulfonate (LAS) contains 20 congeners of linear alkanes (C(10) to C(13)) substituted subterminally with the 4-sulfophenyl moiety in any position from lateral to central. Parvibaculum lavamentivorans DS-1(T) degrades each of eight laterally substituted congeners [e.g., 2-(4-sulfophenyl)decane (2-C10-LAS); herein, compounds are named systematically by chain length (e.g., C(10)) and by the position of the substituent on the chain (e.g., position 2)] to a major sulfophenyl carboxylate [SPC; here 3-(4-sulfophenyl)butyrate (3-C4-SPC)] and two minor products, namely, the alpha,beta-unsaturated SPC (SPC-2H, here 3-C4-SPC-2H) and the SPC+2C (here 5-C6-SPC) species (D. Schleheck, T. P. Knepper, K. Fischer, and A. M. Cook, Appl. Environ. Microbiol. 70:4053-4063). The degradation of centrally substituted congeners by strain DS-1 was examined in this work. 5-C10-LAS yielded not only the predicted 4-C8-SPC, 4-C8-SPC-2H, and 6-C10-SPC (about 70% of products) but also sulfophenyl dicarboxylates (SPdC), i.e., C6-, C8-, and C10-SPdC. These were identified by electrospray ionization-mass spectrometry (ESI-MS) after separation by high-pressure liquid chromatography (HPLC). ESI ion-trap MS and ESI-time of flight-MS were used to confirm the identities of key intermediates. Different mixtures of congeners obtained by separation of commercial LAS by HPLC were degraded, and the degradative products were compared. If a congener carried the sulfophenyl substituent on the 5, 6, or 7 position, SPdCs were formed as well as SPC, SPC-2H, and SPC+2C, whereas the substituent on the 2, 3, or 4 position yielded only SPC, SPC-2H, and SPC+2C. Some 50 products were generated from the 20 LAS congeners: 11 major SPCs, each with an SPC-2H and an SPC+2C (i.e., 33 SPC and SPC-2H species), and about 17 SPdC species. A large array of compounds, many in low quantities, is thus generated by P. lavamentivorans DS-1 during the degradation of commercial LAS.     

发酵碳源对铜绿假单胞菌NY3所产鼠李糖脂结构及性能的影响

为研究发酵碳源对铜绿假单胞菌NY3所产鼠李糖脂结构及性能的影响,从鼠李糖脂的结构组分、性能和应用效果等方面展开研究。薄层实验证明两种鼠李糖脂均含有单糖脂和双糖脂。液质分析发现以橄榄油作碳源时,鼠李糖脂中双糖脂(Rha-Rha-C5-C6:1和Rha-Rha-C8-C8:2)比例更大,约为73.09%。而地沟油作碳源时,单糖脂(Rha-C10-C10和Rha-C16-C16:2)的比例更高,约为76.91%。橄榄油和地沟油为碳源的鼠李糖脂的临界胶束浓度(CMC)分别为55 mg/L和80mg/L。相同投加量时,前者乳化性和乳化稳定性均优于后者。NY3菌降解含油污泥时,投加双糖脂含量高的鼠李糖脂会使C16-C30直链烷烃的去除率更高。     

Chemical structure, surface properties and biological activities of the biosurfactant produced by Pseudomonas aeruginosa LBI from soapstock

Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RL(LBI)) when cultivated on soapstock as the sole carbon source. HPLC-MS analysis of the purified culture supernatant identified 6 RL homologues (%): R(2) C(10) C(10) 28.9; R(2) C(10) C(12:1) 23.0; R(1) C(10) C(10) 23.4; R(2) C(10) C(12) 11.3; R(2) C(10) C(12) 7.9; R(2) C(10) C(12) 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RL(LBI), its physicochemical properties were studied. RL(LBI) had a surface tension of 24 mN m(-1) and an interfacial tension of 1.31 mN m(-1); the cmc was 120 mg l(-1). RL(LBI) produced stable emulsions with hydrocarbons and vegetable oils. This product showed good antimicrobial behaviour against bacteria: MIC for Bacillus subtilis, Staphylococcus aureus and Proteus vulgaris was 8 mg l(-1), for Streptococcus faecalis 4 mg l(-1), and for Pseudomonas aeruginosa 32 mg l(-1). RL(LBI) was active against phytopathogenic fungal species, MIC values of 32 mg l(-1) being found against Penicillium, Alternaria, Gliocadium virens and Chaetonium globosum. Due to its physicochemical properties and antimicrobial behaviour, RL(LBI) could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.     

Monorhamnolipids and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) production using Escherichia coli as a heterologous host

Pseudomonas aeruginosa produces the biosurfactants rhamnolipids and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs). In this study, we report the production of one family of rhamnolipids, specifically the monorhamnolipids, and of HAAs in a recombinant Escherichia coli strain expressing P. aeruginosa rhlAB operon. We found that the availability in E. coli of dTDP-l-rhamnose, a substrate of RhlB, restricts the production of monorhamnolipids in E. coli. We present evidence showing that HAAs and the fatty acid dimer moiety of rhamnolipids are the product of RhlA enzymatic activity. Furthermore, we found that in the recombinant E. coli, these compounds have the same chain length of the fatty acid dimer moiety as those produced by P. aeruginosa. These data suggest that it is RhlAB specificity, and not the hydroxyfatty acid relative abundance in the bacterium, that determines the profile of the fatty acid moiety of rhamnolipids and HAAs. The rhamnolipids level produced in recombinant E. coli expressing rhlAB is lower than the P. aeruginosa level and much higher than those reported by others in E. coli, showing that this metabolic engineering strategy lead to an increased rhamnolipids production in this heterologous host.     

Direct Quantitative Gas Chromatographic Separation of C2-C6 Fatty Acids, Methanol, and Ethyl Alcohol in Aqueous Microbial Fermentation Media

A method is described for the direct quantitative gas chromatographic separation of C(2)-C(6) lower fatty acid homologues, methanol, and ethyl alcohol in aqueous microbial fermentation media. A hydrogen flame detector and a single-phase solid column packing, comprising beads of a polyaromatic resin (polystyrene cross-linked with divinyl benzene), were employed. Direct injections of 1 to 10 muliters of aqueous culture supernatant fluids were made. Quantitative recoveries of C(2)-C(6) acids added to culture supernatant fluids were obtained.     

Formation and degradation of dicarboxylic acids in relation to alterations in fatty acid oxidation in rats.

Dicarboxylic acids are excreted in urine when fatty acid oxidation is increased (ketosis) or inhibited (defects in beta-oxidation) and in Reye's syndrome. omega-Hydroxylation and omega-oxidation of C6-C12 fatty acids were measured by mass spectrometry in rat liver microsomes and homogenates, and beta-oxidation of the dicarboxylic acids in liver homogenates and isolated mitochondria and peroxisomes. Medium-chain fatty acids formed large amounts of medium-chain dicarboxylic acids, which were easily beta-oxidized both in vitro and in vivo, in contrast to the long-chain C16-dicarboxylic acid, which was toxic to starved rats. Increment of fatty acid oxidation in rats by starvation or diabetes increased C6:C10 dicarboxylic acid ratio in rats fed medium-chain triacylglycerols, and increased short-chain dicarboxylic acid excretion in urine in rats fed medium-chain dicarboxylic acids. Valproate, which inhibits fatty acid oxidation and may induce Reye like syndromes, caused the pattern of C6-C10-dicarboxylic aciduria seen in beta-oxidation defects, but only in starved rats. It is suggested, that the origin of urinary short-chain dicarboxylic acids is omega-oxidized medium-chain fatty acids, which after peroxisomal beta-oxidation accumulate as C6-C8-dicarboxylic acids. C10-C12-dicarboxylic acids were also metabolized in the mitochondria, but did not accumulate as C6-C8-dicarboxylic acids, indicating that beta-oxidation was completed beyond the level of adipyl CoA.     

Characterization of a new phosphonocerebroside, N-methyl-2-aminoethylphosphonylglucosylceramide, from the antarctic krill, Euphausia superba

A novel phosphonglycosphingolipid was purified from the whole tissue of the antarctic krill, Euphausia superba by successive column chromatography on DEAE- and QAE-Sephadex and silicic acid (Iatrobeads). The structure was elucidated by means of IR, FAB-MS, 1H-NMR, GC and GC-MS analyses of the water-soluble products after complete and partial acid hydrolysis, and methylation analysis of a product of hydrogen fluoride degradation; it was identified to be a phosphonocerebroside, 6'-O-(N-methyl-2-aminoethylphosphonyl)Glcp beta 1----1ceramide. The ceramide moiety was composed of tetradecasphingenine and octadecasphingatriene as the main sphingoids, and monounsaturated C22- and C24-acids and their 2-hydroxy homologues as the major fatty acids.     

Susceptibility of<Emphasis Type="Italic">Escherichia coli</Emphasis> to C<Subscript>2</Subscript>-C<Subscript>18</Subscript> fatty acids

The antimicrobial activity of C2-C18 fatty acids was determined in vitro in cultures of two strains of Escherichia coli grown on glucose. Antimicrobial activity was expressed as IC50 (a concentration at which only 50% of the initial glucose in the cultures was utilized). Utilization of glucose was inhibited by caprylic acid (IC50 0.30-0.85 g/L) and capric acid (IC50 1.25-2.03 g/L). Neither short-chain fatty acids (C2-C6) nor fatty acids with longer chain (C12-C18) influenced substrate utilization. Caproic acid, however, decreased cell yield in cultures of E. coli in a dose-dependent manner. No inhibition of glucose utilization was produced with unsaturated fatty acids, oleic and linoleic. Calcium ions added in excess reversed the antimicrobial effect of capric acid, but not that of caprylic acid. Antimicrobial activity of caprylic and capric acid decreased when the bacteria were grown in the presence of straw particles, or repeatedly subcultured in a medium containing these compounds at low concentrations. Counts of viable bacteria determined by plating decreased after incubation with caprylic and capric acid (30 min; 1 g/L) at pH 5.2 from > 10(9) to approximately 10(2)/mL. A reduction of a mere 0.94-1.96 log10 CFU was observed at pH 6.5-6.6. It can be concluded that caprylic acid, and to a lesser extent also capric acid, has a significant antimicrobial activity toward E. coli. Effects of other fatty acids were not significant or absent.     

Molecular species of ceramides from the ascomycete truffle Tuber indicum

The ceramide fractions were isolated from the chloroform/methanolic extractable of the fruiting bodies of Tuber indicum and separated into three kinds of molecular species TI-1, TI-2, and TI-3 by normal and reverse phase silica gel-column chromatography. By means of (1)H NMR and (13)C NMR spectroscopy, fast atom bombardment mass spectrometry (FAB-MS), and chemical degradation experiment, their component sphingoid base for TI-1 and TI-2 was uniformly (2S,3S,4R)-2-amino-1,3,4-octadecantriol, while the sphingoid of TI-3 was d-erythro-sphingosine, and their structures have been determined unequivocally to be (2S,2'R,3S,4R)-2-(2'-d-hydroxyalkanoylamino) octadecane-1,3,4-triol, the fatty acid composition of which consists of 2-hydroxydocosanoic, 2-hydroxytetracosanoic, and 2-hydroxytricosanoic acids (from major to minor); (2S,3S,4R)-2-(alkanoylamino)octadecane-1,3,4-triol, the fatty acid composition of which is unusual and consists of docosanoic, hexadecanoic, tricosanoic, octadecanoic and nonadecanoic acids (from major to minor); and (2S,3R,4E)-2-(alkanoylamino)-4-octadecene-1,3-diol, the component fatty acids of which were hexadecanoic (predominant) and octadecanoic acids, respectively.     

Glucosylceramide having a novel tri-unsaturated long-chain base from the spermatozoa of the starfish, Asterias amurensis

Glucosylceramide (Glc beta 1-1Cer) was isolated from the spermatozoa of the starfish, Asterias amurensis. The long-chain bases of the glycolipid consisted of dihydroxy (d18:2, d18:3, d19:3, and d22:2), and trihydroxy (t22:1) types. Long-chain aldehydes derived from them were analyzed mainly by proton nuclear-magnetic resonance to determine the detailed structures. Two of the tri-unsaturated bases were identified as (4E,8E,10E)-2-amino-4,8,10-octadecatriene-1,3-di ol (d18:3) and (4E,8E,10E)-2-amino-9-methyl-4,8,10-octadecatriene+ ++-1,3-diol (d19:3), which is a novel base. Both d22:2 and t22:1 had a cis double bond at the C9 or C13 position. All fatty acids were 2-hydroxylated (C14-C25): Most of them were saturated and unbranched. About 10% was mono-unsaturated and unbranched (C22-C25), while saturated but branched (iso- and anteiso-types) C15-C18 acids were found as minor components. The main fatty acids, which summed up to more than 93% of the fatty acids in the glucosylceramide, were n-14h:0, n-15h:0, n-16h:0, n-17h:0, n-18h:0, and n-24h:1.     

Metabolism of cis-12-octadecenoic acid and trans-9,trans-12-octadecadienoic acid and their influence on lipogenic enzyme activities in mouse liver

High carbohydrate (65% glucose) diets containing cis-12-octadecenoic acid (12c-18:1) or trans-9,trans-12-octadecadienoic acid (9t,12t-18:2) were fed to weanling mice to investigate the influence of fatty acid structure on six hepatic enzyme activities involved in lipid metabolism. Results with these diets were compared to those with diets containing no fatty acids, saturated fatty acids; cis-9-octadecenoic acid (9c-18:1) and cis-9,cis-12-octadecadienoic acid (9c,12c-18:2). These comparisons show saturated fatty acids, 9c-18:1, 12c-18:1, and 9t,12t-18:2, had little or no influence on the activity levels of fatty acid synthetase, malic enzyme (EC 1.1.1.40)citrate cleavage enzyme (EC 4.1.3.8), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and acetyl-CoA carboxylase (EC 6.4.1.2). Neither 12c-18:1 nor 9t,12t-18:2 produced the dramatic enzyme-lowering effect exhibited by the diet containing 9c,12c-18:2 when compared to the diet devoid of fat. Thus, both the 9 and 12 bonds must be present in the same molecule. Also, at least one and probably both bonds must be in the cis configuration to depress liver enzyme activities. Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were both used for analysis of the methyl esters derived from the hepatic lipids. The GC and GC-MS data provided (a) direct evidence for incorporation of both isomers into hepatic lipids and (b) indirect evidence that 9t,12t-18:2 lowered liver delta 9-desaturase activity. In addition, since these products were found in the complex liver lipids, there is no doubt that the various enzymes concerned with activation and acylation utilize both of these isomeric fatty acids as substrates.