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1.
Oleoyl-CoA elongase catalyzes four successive reactions: condensation of malonyl-CoA to oleoyl-CoA, reduction, dehydration,
and another reduction. Evidence supporting this mechanism and the multienzymatic nature of the elongation complex are reported.
A particulate membrane fraction from rapeseed is able to elongate intermediates (R,S) 3-hydroxy-20∶0-CoA and (E) 2,3–20∶1-CoA to very long chain fatty acids in the presence of malonyl-CoA. Studies of the 3-ketoacyl-CoA synthase activities
showed that maximal activity could be measured by using 15 to 30 μM 18∶1-CoA and 30 μM malonyl-CoA, and that 18∶0-CoA and
18∶1-CoA were the best substrates. Comparison of the condensation and the overall elongation activities indicated that condensation
is the rate-limiting step of the elongation process. The 3-hydroxyacyl-CoA dehydratase activity was maximal in the presence
of 75 μM Triton X-100 and 25 μg of proteins. Finally, the acyl-CoA elongase complex was solubilized and purified. During the
purification process, the 3-hydroxyacyl-CoA dehydratase copurified with the elongase complex, strongly suggesting that this
enzyme belongs to the elongase complex. The apparent molecular mass of 700 kDa determined for the elongase complex, and the
fact that four different polypeptide bands were detected after sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis
of the purified fraction, further suggest that the acyl-CoA elongase is a multienzymatic complex. 相似文献
2.
In the present study, we examined the ability of detergents to stimulate and solubilize phospholipase D (PLD) of a particulate
fraction of rat brain. PLD activity was assayed by measuring the [3H]choline produced from the exogenous substrate dipalmitoyl phosphatidyl[3H]choline (dipalmitoyl [3H]PC). In the absence of detergents, PLD activity was not detectable. Of the detergents examined, Triton X-100 was found to
markedly enhance PLD activity, whereas other detergents including sodium doexycholate, sodium cholate, CHAPS and Lubrol-PX
caused only a small, if any increase in activity. Enhancement by Triton X-100 was maximal at 0.1–0.2% (w/v) and decreased
at higher concentrations. The optimal pH was 7.1–7.3. Both Ca2+ and Mg2+ inhibited enzyme activity stimulated by Triton X-100 in a concentration-dependent manner. Triton X-100 effectively solubilized
PLD from the particulate fraction of rat brain; more than 70% of the activity of the particulate fraction was extracted by
0.5–1.0% (w/v) Triton X-100. Furthermore, when the PLD activities in brains of three different species (rat, rabbit and bovine)
were measured under optimal conditions, the activities were found to differ greatly. PLD activity was highest in rabbit brain,
followed by rat and bovine brains; the activity in bovine brain was extremely low compared to the activities in rat and rabbit
brains. We conclude that Triton X-100 is potentially useful for the purification of PLD and that rabbit and rat brains are
the preferred sources. 相似文献
3.
In the Triton X-100/n-CnH2n+1COOH/H2O system, n-CnH2n+1COOH can be used as a cosurfactant. As its chain length increases, the regions of the microemulsions showing oil-in-water
(O/W), water-in-oil (W/O), and bicontinuous structures decrease and at the same time, the region of the lamellar liquid crystal
increases. In the O/W region, the distribution coefficient K of n-CnH2n+1COOH between Triton X-100 micellar phase and water phase increases with the chain length of saturated unbranched monocarboxylic
acid. The relationship between the standard solubilization Gibbs free energy of saturated unbranched monocarboxylic acid and
the number of methylene groups in the saturated unbranched monocarboxylic acid is given by the equation: ΔG
m
0=−2.364−2.818 n(CH2) kJ·mol−1 in the Triton X-100 micellar system. In the lamellar liquid crystal region, small-angle X-ray diffraction shows that the
thickness of the bilayer d
0 is independent of the weight ratio of n-CnH2n+1COOH to Triton X-100, but the volume of the solvent penetrating from the solvent layer to the amphiphilic bilayer increases
with the weight ratio of n-CnH2n+1COOH to Triton X-100. Furthermore, the d
0 value increases with the chain length of saturated unbranched monocarboxylic acid, which will contribute to the formation
and stabilization of the lamellar liquid crystal. 相似文献
4.
The very-long-chain polyunsaturated fatty acid (VLC-PUFA), arachidonic acid (ARA, 20:4ω-6) is a component of neuron tissues
such as brain and retina cells and a primary substrate for the biosynthesis of biologically active eicosanoids. The green
freshwater microalga Parietochloris incisa (Trebouxiophyceae) has been shown to accumulate an extraordinary high content of ARA-rich triacylglycerols. It was thus interesting
to characterize the genes involved in lipid biosynthesis in this alga. We report here the identification of a cDNA encoding
for a P. incisa PUFA elongase (PiELO1) and demonstrate that the expression of PiELO1 in yeast Saccharomyces cereviseae confers its elongase activity on C18 ∆6 PUFA. Phylogenetic analysis indicated that PiELO1 is highly similar to functionally
characterized ∆6 PUFA elongase genes from other green algae and lower plants. Quantitative real-time PCR expression studies
showed that PiELO1 is upregulated under nitrogen starvation, the condition triggering and enhancing storage oil and ARA accumulation in P. incisa. 相似文献
5.
Photosystem I (PS I) particles prepared from pea chloroplasts using either digitonin or Triton X-100 as the solubilizing detergent were used to investigate the EPR characteristics of the electron acceptors A0, A1, and (Fe-S)X. The signal from component A1 appears asymmetric in both digitonin and Triton X-100 solubilized samples. However, the difference spectrum which represents the isolated signal from component A0 is symmetric in Triton X-100 solution, but not in digitonin. Upon deuteration of digitonin solubilized PS I, the signal from A1 became partially narrowed to give a spectrum comparable to that of deuterated Triton X-100 solubilized particles. However, deuteration did not produce new spectral features in the digitonin solubilized preparation, but emphasized those already present Upon storage of either type of particles at 77 K, it was found that the signal from component A1, but not that from A0, decayed. The difference spectrum of A1 obtained with g = 2.0058 and a peak-to-peak linewidth of 0.95 mT is compatible with the identification of A1 as an anionic semiquinone. In digitonin solubilized particles, component A0 and not A1 affected the EPR signal of the iron-sulphur center X, which suggests a magnetic interaction between A0 and X. These results suggest that component A0 is closer to X than is A1, and that A1 may not be in a linear electron transport pathway between A0 and the iron-sulphur centers. They also show that Triton X-100 perturbs the structure of the reaction center. 相似文献
6.
In an attempt to clarify the mechanism of lipid accumulation inMortierella ramanniana var.angulispora, diacylglycerol acyltransferase (DGAT) in the membrane fraction from this fungus was characterized. The enzyme had an optimum
pH of 7.0–7.5, and enzyme activity was blocked by SH-reagents. Metal ions were not essential for maintaining DGAT activity.n-Octyl-β-d-glucoside, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and Tween 80 were found to preserve activity, while
Triton X-100 and sucrose monolaurate inhibited it. As the inhibition of DGAT activity by Triton X-100 was overcome by the
addition of diacylglycerol (DG), the dependency of DGAT activity on exogenous DG was determined in the presence of 0.1% Triton
X-100. DGAT activity in the membrane fraction was traced in fungi cultured for different time periods or in media at different
carbon to nitrogen (C/N) ratios. Although the increase in total lipid content with culture time was accompanied by an increase
in DGAT activity, total lipid changes related to changes in C/N ratio did not correlate with DGAT activity. Factors other
than DGAT activity in the membrane fraction would appear to be involved in the regulation of total lipid content in this fungus. 相似文献
7.
Tung oil is an industrial drying oil containing ca. 90% PUFA. We previously reported on enzymes required for the synthesis of linoleic (6% of FA) and eleostearic (80%) acids
and here describe the cloning and functional analysis of an omega-3 FA desaturase (FAD3) required for the synthesis of linolenic
acid (1%). The tung FAD3 cDNA was identified by screening a tung seed cDNA library using the polymerase chain reaction and
degenerate primers encoding conserved regions of the FAD3 enzyme family. Expression of this cDNA in yeast cells, cultured
in the presence of linoleic acid, resulted in the synthesis and accumulation of linolenic acid, which accounted for up to
18% w/w of total cellular FA. Tung FAD3 activity was significantly affected by cultivation temperature, with the greatest
amount of linolenic acid accumulating in yeast cells grown at 15°C. The amount of linolenic acid synthesized in yeast cells
by tung FAD3 is ca. 10-fold higher than that observed by expression of a rapeseed (Brassica napus) FAD3 in yeast, suggesting that tung FAD3 might be useful for biotechnological production of omega-3 FA in transgenic organisms. 相似文献
8.
The solubilization and partial purification of cholinephosphotransferase (CDPcholine:1,2-diacylglycerol cholinephosphotransferase,
EC 2.7.8.2) from rat liver microsomes were examined in the presence of ionic (sodium deoxycholate), nonionic (Triton X-100,n-octylglycoside), or zwitter ionic (CHAPS) detergents. Among the four detergents tested, only sodium deoxycholate was found
to be an efficient solubilizer of cholinephosphotransferase activity from microsomal membranes, whereas the other three detergents
caused irreversible inactivation of the enzyme at the solubilization step. Addition of phospholipids at the solubilization
step, or after solubilization of the membrane proteins, could not preserve or reconstitute activity to any extent. The sodium
deoxycholate-solubilized activity was partially purified by gel permeation chromatography (Superose 12HR). The partially purified
preparation appeared to consist of a large aggregate containing phospholipids; further dissociation of the protein-phospholipid
complex caused complete inactivation of the enzyme. The partially purified cholinephosphotransferase showed a specific activity
of 100–130 nmol/min/mg protein, which is the highest activity reported to date from any tissue source; this amounts to a 4-fold
enrichment of cholinephosphotransferase activity from the original KCl-washed rat liver microsomes. Ethanolaminephosphotransferase
(CDPethanolamine:1,2-diacylglycerol ethanolaminephosphotransferase, EC 2.7.8.1) activity was copurified and 6-fold enriched
with a total recovery of 60%. During the purification of cholinephosphotransferase activity, a putative endogenous inhibitor
of cholinephosphotransferase was also solubilized and was isolated from the microsomal membranes. This heat-labile, nondialyzable
inhibitor was shown to act specifically on cholinephosphotransferase and not on ethanolaminephosphotransferase. Further characterization
of the inhibitory activity revealed that it may act at the binding step of the cholinephosphotransferase to its lipid substrate,
diacylglycerol. 相似文献
9.
The sialytransferase(s) that transfers sialic acid to lacto-N-neotetraosylceramide and other glycosphingolipids with a galactose nonreducing terminus has been successfully solubilized
from embryonic chicken skeletal muscle. The enzyme can be stored in 50 mM HEPES (pH 6.8), 1% Triton CF-54, and 20% glycerol
at −70°C for as long as six months. Addition of phosphatidylcholine or sphingomyelin (0.167%) readily reactivates the stored
inactive enzymes and such activity persists for about two weeks at 0°–4°C with the peak activity occurring at 1 to 2 days.
Sphingomyelin from chicken muscle, which contains mainly C16∶0 and C18∶0, is 2.1-fold more effective than bovine brain sphingomyelin
at the same concentration (0.4%).
Abbreviations: GM3, GM1, GD1a, GD1b, GT1b were designated according to Svennerholm, L. (1963)J. Neurochem. 10, 613–623. GgOse4Cer and nLcOse4Cer are short designations recommended by the IUPAC-IUB Commission on Lipid Nomenclature (1977)Eur. J. Biochem. 79, 11–21. Other abbreviations used are IV3 NeuAcnLcOse4Cer; nLcOse6Cer, V4Gal, IV3 GlcNAc-nLcOse4Cer; NeuAc-nLcOse6Cer, VI3 NeuAc, V4 Gal, IV3 GlcNAc-nLcOse4Cer; PC, phosphatidylcholine; SM, sphingomyelin, SAT, sialyltransferase; Hepes, 4-2(hydroxyethyl)1-piperazineethane sulfanic
acid. Structures of glycolipids: nLcOse4Cer, Gal(β1→4)GlcNAc(β1→3)Gal(β1→4)-GlcCer; GgOse4Cer, Gal(β1→3)GalNAc(β1→4)Galβ(1→4)GlcCer. 相似文献
10.
Olefinic fatty methyl esters, undec-10-enoate (1), octadec-Z-9-enoate (2), methyl-12 hydroxy octadec-Z-9-enoate (3), on reaction with N-halosuccinimides (4,5), that is, N-bromosuccinimide (4) or N-chlorosuccinimide (5) and 2-mercaptoethanol (6) in benzene, gave β-bromo- or β-chlorothioethoxylates (8–13). β-Halothioethoxylates so formed were acetylated with acetyl chloride in CH2Cl2 to form the respective acetylated products (20–25). 相似文献
11.
Reaction selectivities were determined in multicompetitive reactions mediated by Rhizomucor miehei (RM) lipase at water activity of 0.19 in hexane. Saturated FA (C4–C18 even chain) and oleic acid (C18∶1) were reacted with
a single alcohol, glycerol, or α-or β-MAG containing C4, C10, C16, or C18∶1 individually as alcohol cosubstrate. Similar patterns
of broad FA selectivity toward C8–C18 FA were generally observed for esterification into specific acylglycerol (AG) pools
with the different α/β-CX-MAG cosubstrates. Exceptions were enrichment of C18 in the MAG pool with α-C16-MAG substrate, and
a general suppression of C4/C6 FA reactivity and a specific discrimination toward >C8 FA incorporation into the TAG pool,
both for reactions with α-C10- and α-C16-MAG. RM lipase selectivity toward MAG was in descending order: β-C18∶1-MAG>α/β-C4-MAG∼β-C10-MAG∼β-C16-MAG>α-C18∶1-MAG
>α-C10-MAG∼α-C16-MAG. Selectivity in channeling CX of the original CX-MAG substrates into higher AG species was in descending
order: α-C10-MAG∼α-C16-MAG>β-C10-MAGβ-C16-MAG>α-C18∶1-MAG>β-C18∶1-MAG∼ α/β-C4-MAG. Aside from their characteristic FA selectivity,
Burkholderia cepacia (PS-30) and RM lipases behaved similarly in terms of MAG selectivity as well as a general conservation of FA selectivity
throughout the sequential steps of TAG assembly from FA and glycerol for processes designed to yield specifically structured
TAG. 相似文献
12.
Olefinic fatty methyl esters [undec-10-enoate (1), octadec-Z-9-enoate (2), methyl-12 hydroxy octadec-Z-9-enoate (3)], on reaction with an N-halosuccinimide (4–5)—i.e., N-bromosuccinimide (NBS; 4) or N-chlorosuccinimide (NCS; 5)—in the presence of diols such as mono-, di-, tri-, and tetraethylene glycols (6–9), gave the respective β-bromo- or β-chloroethoxylates (11–34). 相似文献
13.
Robert L. Wolff 《Journal of the American Oil Chemists' Society》1992,69(2):106-110
The fatty acid compositions of rapeseed and soybean oils marketed in France have been determined by gas liquid chromatography
on a fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary phase. Under the operating conditions
employed, methyl esters of linolenic acid geometrical isomers could be separated and quantitated easily without any other
complementary technique. With only one exception, all samples under study (eight salad oils and five food samples) contain
geometrical isomers of linolenic acid in measurable, although variable, amounts. Totaltrans-18:3 acids may account for up to 3% of total fatty acids. This value corresponds to a degree of isomerization (percentage
oftrans isomers relative to total octadecatrienoic acids) of 30%. Examination of our data indicates that the distribution pattern
of linolenic acid geometrical isomers does not depend on the degree of isomerization. The two main isomers always have thec,c,t and thet,c,c configurations. These isomers occur in the almost invariable relative proportions of 47.8±1.7% and 41.1±1.0%, respectively.
The third mono-trans isomer is present in lower amounts−6.5±0.7%. The only di-trans isomer that can be quantitated with sufficient accuracy is thet,c,t isomer (4.9±1.5%). Mono-trans isomers of linoleic acid are also present in these oils. However, their maximum percentages are lower than those determined
for linolenic acid geometrical isomers. In the oils showing the highest degrees of isomerization,trans isomers of linoleic acid account for 0.5% (rapeseed oils) and 1% (soybean oils) of total fatty acids. Taking into account
all data, it would appear that the probability of isomerization of linolenic acid is about 13–14 times that of linoleic acid. 相似文献
14.
Cessation of polyunsaturated fatty acid formation in four selected filamentous fungi when grown on plant oils 总被引:6,自引:0,他引:6
Four fungi,Conidiobolus nanodes, Entomophthora exitalis, Mortierella isabellina, andMucor circinelloides, were grown on various oils (triolein, sesame, safflower, linseed, and oil fromM. isabellina) and produced lipids in which the fatty acids were predominantly the same as those of the original staring substrate. Only
in the first two cases was there evidence of a small amount of chain elongation and of fatty acid desaturation taking place.
The extent of this was only about 10% of that seen in glucose-grown cells. The apparent repression of the fatty acid desaturases
and elongases was not reversed by growing cells on glucose and oils as mixed substrates—the fatty acid profiles were the same
as when the fungi had grown in oils alone. Neither was the cessation of polyunsaturated fatty acid synthesis due to the presence
of nonoil components (NOC) in the oil. Only the NOC from sesame oil affected one single conversion, that of 20∶3n-3 to 20∶4n–6.
We conclude that fatty acid desaturase and elongase systems are repressed either partially or completely in a filamentous
fungi grown on triacylglycerol oils. 相似文献
15.
J. Kevin Polman Karen S. Miller Daphne L. Stoner Cynthia R. Breckenridge 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,61(1):11-17
Tween 80 (polyoxyethylene sorbitan monooleate), Triton X-100 (nonaethylene glycol octylphenol ether), and SDS (sodium dodecyl sulfate) solubilized several components of Mississippi Wilcox lignite and Illinois No. 6 bituminous coal. Tween 80 extraction of alkali-soluble Ugljevik lignite resulted in an increase in hydrogen content and decreases in the nitrogen and sulfur contents of undissolved coal solids. Biosurfactant-containing cell-free extracts of Bacillus licheniformis solubilized a 53 000 Da coal component of Mississippi Wilcox lignite. The results suggest that solubilization of coal organic components by chemically- and biologically-synthesized surfactants has potential in terms of upgrading coals. 相似文献
16.
R. Ap. Ferrari W. Esteves K. D. Mukherjee 《Journal of the American Oil Chemists' Society》1997,74(2):93-96
Steryl ester content of refined and interesterified corn, soybean, and rapeseed oils has been measured via clean-up on a short silica gel column, followed by high performance liquid chromatography with evaporative light-scattering
mass detector. Chemical interesterification, catalyzed by sodium methoxide, led to random positional distribution of fatty
acids in triacylglycerols and some increase in the steryl ester content of all three oils. Enzymatic interesterification,
catalyzed by the immobilized lipase from Rhizomucor miehei (Lipozyme), resulted in a distinct reduction in steryl ester content, but essentially no alteration in positional distribution
of fatty acids in triacylglycerols occurred. Formation of steryl esters during chemical and enzymatic interesterification
was also examined by radioactive tracer technique with [4-14C]β-sitosterol added as marker to refined rapeseed oil and measurement of the radioactive steryl esters formed. Chemical interesterification
of rapeseed oil resulted in moderate formation (10% of total radioactivity) of radioactive β-sitosteryl esters. Enzymatic
interesterification of the oil, catalyzed by Lipozyme, led to little formation of radioactive β-sitosteryl esters, whereas
with the lipase from Candida cylindracea high proportions (>90% of total radioactivity) of 14C-labeled β-sitosteryl esters were formed.
Part of doctoral thesis of Roseli Ap. Ferrari to be submitted to Faculdade de Engenharia de Alimentos, Universidade de Campinas,
Campinas, Brazil. 相似文献
17.
Effects of expansion of the hepatic free cholesterol pool on bile acid and cholesterol metabolism and homeostasis were examined
in rats fed cholesterol in high-fat diets or treated with oleyl-p-(n-decyl)-benzenesulfonate (ODS) or progesterone. Cholesterol feeding for 10–16 days, which increased free (33%) and esterified
(6-fold) cholesterol, had no effect on cholate synthesis, total bile acid synthesis, or cholate turnover, whereas these activities
were increased 60–80% by ODS and progesterone, which produced only small increases (19%) in free cholesterol. Cholesterol
feeding reduced β-hydroxy-β-methylglutaryl (HMG)-CoA reductase (72%) and cholesteryl ester hydrolase (48%) and increased acyl-CoA:cholesterol
acyltransferase (184%), whereas ODS and progesterone reversed these compensatory responses in cholesterol-fed rats. Cholesterol
7α-hydroxylase was changed no more than 22% by any treatment. A bolus of ODS elevated biliary cholesterol output 41% and shifted
biliary bile acid synthesis and composition toward 12-deoxy bile acids. These effects were not seen in ODS-fed or progesterone-treated
rats, in which cholesteryl ester stores were depleted. It is concluded that effects of free cholesterol on bile acid synthesis
and biliary cholesterol are probably mediated by specific precursor or regulatory pools which can be independently regulated
and which represent a relatively small fraction of hepatic free cholesterol. 相似文献
18.
Yan Liu Wanping Guo X. S. Zhao Juan Lian Jian Dou Fethi Kooli 《Journal of Porous Materials》2006,13(3):359-364
Zeolite β with Si/2Al ratios of 60, 100, and 200 were synthesized using tetraethlammonium hydroxide (TEAOH) as the structure-directing
agent (SDA) in the absence of alkali metal cations. Pt, Pd and Pt-Pd catalysts supported on the zeolite β samples were studied
in n-heptane (n-C7) hydroisomerization. The Pt/β catalysts showed a higher catalytic activity than the Pd/β catalysts. For the Pt/β with
a Si/2Al ratio of 100, its n-C7 conversion and selectivity of C7 isomers were observed to be 87.06% and 75.48% respectively at 250∘C. The activity of n-C7 conversion was stable for at least 82 h. However, the selectivity of C7 isomers was gradually decreased with the reaction
time. Experimental data also showed that the addition of Pd to catalyst Pt/β enhanced the n-C7 conversion, but lowered the selectivity of C7 isomers. Pd catalyst was also observed to minimize the formation of aromatics
in comparison with Pt catalyst. 相似文献
19.
Cheng Jung Tsai Wu Feng Li Bonnie Sun Pan 《Journal of the American Oil Chemists' Society》2008,85(8):731-737
The lipoxygenase (LOX) of the marine green alga Ulva fasciata was purified and immobilized in order to improve the stability and reusability. The algal LOX was partially purified by fractionation
with 35–55% saturation of ammonium sulfate and MacroPrep high Q anion exchange chromatography. The LOX was purified ten times
using linoleic acid (C18:2) or arachidonic acid (C20:4) as substrate, the Michaelis constant (K
m) of LOX was 117.6, 31.3 μM, and maximum velocity (V
max) was 12.8, 23.3 μmol hydroperoxy fatty acid/min-mg protein, respectively. The algal LOX showed the highest activity towards
C18:4 followed by C20:4, C18:2 and methyl ester of C18:4. LOX activity increased up to 10.5 times with increased concentration of Triton X-100 in the extraction medium reaching an
optimum at 0.05%. Calcium chloride, glutathione and phenylmethylsulphonyl fluoride were found effective protectants to LOX
during purification. Hydroperoxyeicosatetraenoic acid (HpETE) formed from arachidonic acid catalyzed by this purified algal
LOX was reduced and identified as 11-hydroxy-5,8,12,14-eicosatetraenoic acid (11-HETE) by NP-HPLC and GC–MS. This algal 11-LOX
was immobilized in alginate beads. The stability was sevenfold greater than that of the unbound lipoxygenase at 4 °C in 0.05 M
Tris–HCl buffer (pH 7.5). This is the first report on immobilization of a marine algal lipoxygenase with a view to its potential
role in seafood flavor formation. 相似文献
20.
Lu-Te Chuang Amanda E. Leonard Jim-Wen Liu Pradip Mukerji Tammy M. Bray Yung-Sheng Huang 《Lipids》2001,36(10):1099-1103
Conjugated linoleic acid (CLA; 18∶2) refers to a group of positional and geometric isomers derived from linoleic acid (LA;
Δ9, 12–18∶2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and
100 μM) on elongation of LA (25 μM) to eicosadienoic acid (EDA; Δ11,14–20∶2). Among four available individual CLA isomers,
only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration
of CLA added to the medium. In the meantime, only these two isomers, when added at 50 μM to the media, were elongated to conjugated
EDA (c11,t13- and t12,c14–20∶2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation
is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and
a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on Δ6-desaturation as
well as elongation of LA which results in a decrease in long-chain n−6 fatty acids and consequently the eicosanoid synthesis. 相似文献