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PubMed1986

Rates of dissolution and biodegradation of water-insoluble organic compounds.

We conducted a study of the relationship between the dissolution rates of organic compounds that are sparingly soluble in water and the biodegradation of these compounds by mixed cultures of bacteria. The rates of dissolution of naphthalene and 4-chlorobiphenyl were directly related to their surface areas. The bacteria caused a decline in the concentration of the soluble substrate. The rate of bacterial growth fell abruptly when 4-chlorobiphenyl or naphthalene was no longer detectable in solution. The population continued to increase in media with different surface areas of insoluble 4-chlorobiphenyl, but the final counts were higher in media in which the surface areas of the substrate were larger. The rates of dissolution of palmitic acid, octadecane, di(2-ethylhexyl) phthalate, and 1-naphthyl N-methylcarbamate were determined in the absence of microorganisms. A mixed culture of microorganisms mineralized palmitic acid, di(2-ethylhexyl) phthalate, and Sevin (1-naphthyl N-methylcarbamate) at a logarithmic rate, but octadecane mineralization was linear. The rates of mineralization at the end of the active phase of the biodegradation were lower than the rate of dissolution of palmitic acid but higher than the rate of dissolution of octadecane in the uninoculated medium. We suggest that spontaneous dissolution rates are only one of the factors that govern the rates of biodegradation.

Alkanes↗
PubMed1980

Effects of ascorbic acid, vitamin E, and fatty acids on lipid composition in cockerels.

Serum, aorta, heart, and liver tissues of cockerels reflected numerous changes in cholesterol and triglyceride composition when 5 or 10% oleic or palmitic acid, ascorbic acid, and vitamin E were added to their diets. Heart cholesterol concentration and liver cholesteryl ester content increased with the 10% oleic acid diet. Heart and liver cholesterol increased when ascorbic acid was added to 5% fatty acid diets, and heart cholesterol increased when ascorbic acid was added to the 10% palmitic acid diet. Vitamin E exerted a cholesterol- or cholesteryl ester-lowering effect on both 10% palmitic and 10% oleic acid diets. Heart and liver triglycerides were lower with the 5% oleic acid diet than with the 5% palmitic acid diet. The opposite effect was observed with the 10% fatty acid diet. Dietary ascorbic acid appeared to have some triglyceride-lowering effect. Dietary fatty acid composition was reflected in cockerel aorta, heart, liver, and serum fatty acid distribution, with oleic acid having the greater influence.

Animals↗
PubMed2000

Selective fatty acid release from intracellular phospholipids caused by PCBs in rat renal tubular cell cultures.

The purpose of this study was to explore the influence of different polychlorinated biphenyls (PCBs) upon the release of oleic and palmitic acid from the intracellular lipids, which were previously labeled with [3H]oleic or [3H]palmitic acid, respectively. Studies have been realized with Aroclor 1248 (a commercial PCB mixture with 48% chlorine by weight), and two pure PCB congeners: 3,3',4, 4'-tetrachlorobiphenyl (a non-ortho-substituted planar congener) and 2,2',4,4',5,5'-hexachlorobiphenyl (a di-ortho-substituted nonplanar congener). The treatment of cells with Aroclor 1248 increased [3H]oleic acid release in a concentration-dependent manner. Our results showed that only the di-ortho-substituted congener which prefers a nonplanar configuration stimulated the release of [3H]oleic acid from the intracellular phospholipids to the culture medium, while the exposure of cell cultures to the chosen non-ortho-substituted coplanar congener did not alter the release of [3H]oleic acid to the culture medium. Finally, none of the PCBs studied could increase the release of [3H]palmitic acid from the intracellular stores significantly. The possibility that these differential alterations in the fatty acid release affect cell function during PCB exposure should therefore be postulated.

Animals↗
PubMed1986

Effect of lipid admixtures on the L-dipalmitoylphosphatidylcholine subtransition.

The effect of lipid admixtures on the properties of the L-dipalmitoylphosphatidylcholine (L-DPPC) subtransition is investigated by using high-sensitivity differential scanning calorimetry. The four admixtures used are D-DPPC, L-dipalmitoylphosphatidylethanolamine (L-DPPE), cholesterol, and palmitic acid. In all cases the subtransition decreases in enthalpy until disappearance with increase of the admixture concentrations. About 5-7 mol% of D-DPPC or palmitic acid are sufficient for abolishment (without position shifts) of the subtransition, while, on addition of L-DPPE or cholesterol, it persists up to about 20 mol% of the admixture and its disappearance is accompanied by a slight shift to higher temperatures. These data are tentatively interpreted in terms of lateral mixing of L-DPPC and admixture as indicating compound formation with D-DPPC and palmitic acid, and clustering of L-DPPE and cholesterol.

Calorimetry, Differential Scanning↗
PubMed1987

The effect of sn-2 fatty acid substitution on phospholipase C enzyme activities.

The human monocyte cell line U937 expresses phospholipase A2 and phospholipase C activities and produces eicosanoids. The phospholipase C (PLC) activity exhibits substrate preference for phosphatidyl-choline (PC), rather than phosphatidylinositol or phosphatidylethanolamine. In order to characterize the PLC activity found in these cells, the effects of substitution of the sn-2 fatty acid on this activity were examined. PC substrates with palmitic acid (PC-2P), oleic acid (PC-2O), arachidonic acid (PC-2A) and linoleic acid (PC-2L) at the sn-2 position were used. The sn-1 fatty acid was palmitic acid. PC-2L and PC-2A with the longer-chain less-saturated fatty acids linoleic acid and arachidonic acid esterified at sn-2 were found to be better substrates for PLC activity than PC-2P or PC-2O in these cells. This preference was maintained even when substrate phospholipid was solubilized in non-ionic, anionic, cationic and zwitterionic amphiphiles. Furthermore, when a 500-fold excess of 1,2-diolein or 1,2-dipalmitin was added to the reaction, the specificity of the PLC activity for PC-2A and PC-2L remained unchanged. When similar experiments were performed with phosphatidylinositol as a substrate, we did not observe any effect when the sn-2 position was altered. These data show that the fatty acid constituent at the sn-2 position affects the observed PLC activity when phosphatidylcholine, but not phosphatidylinositol, is used as a substrate by these cells.

Binding Sites↗
PubMed1995

Localization of the palmitoylation site in the transmembrane protein p12E of Friend murine leukaemia virus.

Friend murine leukaemia virus complex was propagated on murine cells in the presence of [9,10-3H]palmitic acid. Virus particles were harvested from the culture supernatant and lysed with detergents. The viral transmembrane protein, p12E, was isolated from the lysates by size-exclusion chromatography and purified by narrowbore reverse-phase HPLC. Analysis of the purified product by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) revealed that the protein is palmitoylated carrying one fatty acid residue. The radiolabelled fatty acid was released by hydroxylamine treatment at pH 7, indicating that acylation occurred via a thioester linkage. For allocation of the acylation site, p12E was digested with trypsin. The resulting peptides were either directly subjected to MALDI-TOF-MS or fractionated by microbore reverse-phase HPLC prior to mass spectrometry. The results revealed that p12E of Friend murine leukaemia virus is acylated at a cysteine residue situated at the C-terminal side of the putative transmembrane anchor of the polypeptide. Fatty acid analysis of the purified acylpeptide demonstrated that p12E carries almost exclusively palmitic acid.

Acylation↗
PubMed1996

Postparturition changes in the triacylglycerols of cow colostrum.

The changes in the triacylglycerol (TAG) composition of colostrum fat of three cows were studied. In addition to the determination of fatty acid composition by gas chromatography, the distribution of TAG according to the acyl carbon number (ACN) and molecular weight was analyzed utilizing both supercritical fluid chromatography (SFC) and ammonia negative-ion chemical ionization mass spectrometry (MS). Colostrum TG contained substantially less stearic and oleic acids and more myristic and palmitic acids than the normal Finnish milk fat. The major trends in the changes of fatty acids and TAG were similar for each cow, although clear differences between individuals were found. During the first week of parturition, the proportions of short-chain fatty acids (C4-C10) typically increased as well as those of stearic and oleic acids, whereas the relative amounts of C12-C16 acids decreased, especially those of myristic and palmitic acids. Distinct changes occurred also in TAG distributions: the proportions of molecules with ACN 38-40 increased and those with ACN 44-48 decreased. Although there were distinct differences between individuals shortly after delivery, both the fatty acid compositions and TAG distributions of the milk samples of the cows started to resemble each other after one week. The theoretical profiles of colostrum TAG calculated based on the fatty acid compositions differed clearly from the ACN distributions analyzed by SFC and MS. Thus, the analysis of TAG is essential, because the changes in molecular species composition of colostrum TAG cannot be estimated according to the fatty acid analysis alone.

Animals↗
PubMed1990

RAS2 protein of Saccharomyces cerevisiae undergoes removal of methionine at N terminus and removal of three amino acids at C terminus.

RAS2 protein of Saccharomyces cerevisiae undergoes post-translational modifications involving methyl esterification and palmitic acid addition, resulting in their association with the plasma membrane. In this paper, we provide evidence that two kinds of proteolytic events accompany the biosynthesis. This is shown by separating and characterizing three intracellular forms of RAS2 protein: precursor, intermediate, and mature (fatty acid-acylated) forms. N-Terminal sequencing has revealed that all three forms start with proline, which is the second amino acid expected from the RAS2 gene sequence. Thus, the first methionine is removed very early during the biosynthesis. Isolation and sequencing of C-terminal peptides indicate that three C-terminal amino acids present in the precursor form are removed in the intermediate and in the fatty acid acylated forms. C-Terminal proteolysis appears to accompany methyl esterification, since the methylation occurs with the intermediate and the fatty acid-acylated forms, but not with the precursor. Palmitic acid is identified as the major fatty acid attached to the fatty acid-acylated form.

Acylation↗
PubMed1984

In vitro synthesis of mycolic acids by the fluffy layer fraction of Bacterionema matruchotii.

Biosynthetic activity for mycolic acid occurred in the fluffy layer fraction but not in the 5000g supernatant of Bacterionema matruchotii. With [1-14C]palmitic acid as precursor for the in vitro system, the predominant product was identified as C32:0 mycolic acid by radio-gas-liquid chromatographic (radio-GLC) and gas chromatographic/mass spectroscopic analyses; if [1-14C]stearic acid was used, two major radioactive peaks appeared on GLC: one corresponding to the peak of (C34:0 + C34:1) mycolic acids and the other to (C36:0 + C36:1) mycolic acids. By pyrolysis/radio-GLC analysis, C32:0 mycolic acid synthesized by [1-14C]palmitic acid was pyrolyzed at 300 degrees C to form palmitaldehyde (the mero moiety) and methyl palmitate (the branch moiety). The pH optimum for the incorporation of [1-14C]palmitate into bacterionema mycolic acids was 6.4 and the reaction required a divalent cation. The in vitro system utilized myristic, palmitic, stearic and oleic acids (probably via their activated forms) well as precursors, among which myristic and palmitic acids were more effective than the rest. Avidin showed no effect on the biosynthesis of mycolic acid from 14C-palmitate whereas cerulenin, a specific inhibitor of beta-ketoacyl synthetase in de novo fatty acid synthesis, inhibited the reaction at a relatively higher concentration. Thin-layer chromatographic analysis of lipids extracted from the reacting mixture without alkaline hydrolysis showed that both exogenous [1-14C]fatty acid and synthesized mycolic acids were bound to an unknown compound by an alkali-labile linkage and this association seemed to occur prior to the condensation of two molecules of fatty acid.

Actinomycetaceae↗
PubMed1984

Temperature-induced changes in the hydroxy and non-hydroxy fatty acid-containing sphingolipids abundant in the surface membrane of Tetrahymena pyriformis NT-1.

Sphingolipids make up 30 to 40 mole % of the phospholipids found in the surface membrane of Tetrahymena pyriformis NT-1. We have identified the two major classes as non-hydroxy fatty acid-containing ceramide-2-aminoethylphosphonate (NCAEP) and alpha-hydroxy fatty acid-containing ceramide-2-aminoethylphosphonate (HCAEP). Both classes were well represented in cells grown at 39 degrees C. At this temperature their principal long chain bases were n-hexadeca-4-sphingenine and n-nonadeca-4-sphingenine. The major fatty acid of NCAEP from 39 degrees C-grown cells was palmitic acid and that of HCAEP was alpha-hydroxypalmitic acid. Cells grown at 15 degrees C contained NCAEP, but only traces of HCAEP. By analyzing the incorporation of [1-14C]palmitic acid into cells growing isothermally or shifted from 15 degrees C to 39 degrees C, we obtained evidence favoring a direct conversion of NCAEP to HCAEP. This conversion was blocked in cells grown at 15 degrees C, causing an accumulation of NCAEP. Tetrahymena is a useful model system for studying the poorly understood alpha-hydroxylation process that is of critical importance in myelination of animal nervous tissues.

Animals↗
PubMed1997

Phospholipid metabolism in boar spermatozoa and role of diacylglycerol species in the de novo formation of phosphatidylcholine.

We have investigated pathways of lipid metabolism in boar spermatozoa sperm cells incubated for up to 3 days with [14C]palmitic acid, [14C]glycerol, [14C]choline, or [14C]arachidonic acid or incorporated these precursors into diglycerides and/or phospholipids. When spermatozoa were incubated with [14C]palmitic acid or [14C]glycerol, there was first an incorporation into phosphatidic acid, followed by labelling of 1,2-diacylglycerol (DAG) and then phosphatidylcholine (PC). This indicates that the de novo pathway of phospholipid synthesis is active in these cells. However, not all DAG was converted to PC. A pool of di-saturated DAG, which represented a considerable proportion of the high basal levels of DAG, accumulated the majority of label. Another DAG pool, containing saturated fatty acids in position 1 and unsaturated fatty acids in position 2 and representing the remaining basal DAG, was in equilibrium with PC. When spermatozoa were incubated with [14C]arachidonic acid, there was a considerable incorporation of label into PC, which indicates the presence of an active deacylation/ reacylation cycle. The behaviour of certain lipid pools varied depending on the temperature at which spermatozoa were incubated. For example, in the presence of [14C]palmitic acid or [14C]arachidonic acid, there was more incorporation of label into PC when spermatozoa were incubated at 25 degrees C than when incubated at 17 degrees C. Taken together, these results indicate that spermatozoa have an active lipid synthetic capacity. It may therefore be possible to design methods to evaluate the metabolic activity of boar spermatozoa based on the incorporation of lipid precursors under standardized conditions.

Animals↗
PubMed2002

Saturated triglycerides and fatty acids activate neutrophils depending on carbon chain-length.

BACKGROUND: Unsaturated fatty acids are known as neutrophil activators. In the present study we investigated whether saturated triglycerides and fatty acids may also contribute to the previously observed activation of neutrophils by nutritional lipid emulsions. Furthermore we tested the hypothesis that carbon-chain length is of importance in this respect. MATERIALS AND METHODS: Neutrophils (1 x 10(6) mL(-1)) were isolated from the blood of nine volunteers. Chemiluminescence was used to evaluate neutrophil activation, characterized by the production of oxygen radicals by neutrophils during incubation with 1 mmol L(-1) saturated fatty acid (6-20 carbon) or triglycerides (6-12 carbon fatty acid), dissolved in aqueous medium by preparing micelles with dipalmitoyl phosphatidylcholine (DPPC). Results were expressed as means +/- SEMs of the overall luminescence signal relative to the signal of cells incubated in medium. RESULTS: Similar to a positive control, the polyunsaturated fatty acid arachidonic acid (C20 : 4), the triglycerides tricaproin (TC6 : 0), tricaprylin (TC8 : 0) and trilaurin (TC12 : 0) as well as the fatty acids lauric acid (C12 : 0), palmitic acid (C16 : 0), stearic acid (C18 : 0) and arachidic acid (C20 : 0) all induced oxygen radical production in neutrophils, while the medium-chain triglyceride tricaprin (TC10 : 0) and fatty acids caproic acid (C6 : 0), caprylic acid (C8 : 0) and capric acid (C10 : 0) exerted no clear effects, similar to negative controls (DPPC and glycerol). CONCLUSIONS: Besides their (poly)-unsaturated counterparts, saturated triglycerides and fatty acids also activate neutrophils. Carbon chain-length is pivotal in the interaction of fatty acids and triglycerides and cells of the immune system.

Adult↗
PubMed1992

Uptake of palmitate by hepatocyte suspensions: facilitation by albumin?

Albumin-dependent uptake of unbound [3H]palmitic acid by hepatocytes isolated from female rat livers was studied and the experimental results compared with the predictions of a noncompartmental diffusion-reaction theory for the cellular uptake of protein-bound ligands. The outright theoretical predictions involve values for the parameters of the system, some newly measured (hepatocyte radii and the rate constant for the dissociation of palmitate-albumin complex) and some taken from the literature (diffusion coefficients and the equilibrium association constant for the palmitate-albumin complex). The measured unbound clearance of [3H]palmitic acid, defined as the initial uptake velocity divided by the unbound [3H]palmitic acid concentration in the medium, was enhanced 6.6-fold as the concentration of human serum albumin was increased from approximately 5 to 480 microM. This enhancement factor was predicted by the theory, according to which the enhancement reflects codiffusion of bound ligand across the unstirred layer adjacent to the cell membrane and, therefore, an increased delivery of unbound ligand to the cell surface. In contrast, the absolute magnitude of the unbound clearance was consistent with the theory only for the lowest published value for the equilibrium association constant, 15 microM-1. For higher published values (62 and 94 microM-1), the magnitude of the unbound clearance observed experimentally was severalfold higher than that predicted by the theory. If in fact the association constant exceeds 30 microM-1, the data would imply that an albumin-dependent facilitation mechanism exists which enhances the availability of palmitate to the cell over and above the enhancement predicted by the diffusion-reaction theory.

Animals↗
PubMed2004

Evidence that palmitoylation of carboxyl terminus cysteine residues of the human luteinizing hormone receptor regulates postendocytic processing.

Palmitoylation is a well-conserved posttranslational modification among members of the G protein-coupled receptor superfamily. The present study examined the role of palmitoylation in endocytosis and postendocytic trafficking of the human LH receptor (LHR). Palmitoylation of the LHR was determined by incorporation of [3H]palmitic acid into wild-type (WT) or mutant receptor in which the potential palmitoylation sites, C643 and C644, were mutated to glycine residues. The WT receptor showed incorporation of [3H]palmitic acid into the mature 90-kDa form of the receptor whereas mutation of the two Cys residues abrogated this incorporation, indicating that Cys 643 and C644 are the sites of palmitoylation. The role of palmitoylation on endocytosis and postendocytic processing was examined by testing the ability of the WT and mutant receptor to undergo internalization, recycling, and lysosomal degradation. Compared with the WT receptor, the mutant receptor showed increased internalization and decreased recycling, suggesting that retention of palmitic acid residues at Cys 643 and 644 promotes LHR recycling. The role of palmitoylation on receptor recycling was substantiated by demonstrating that a different mutant, D578H LHR, which is deficient in palmitoylation, also recycled less efficiently. Furthermore, the data show that palmitoylation, not the rate of internalization, determines the efficiency of recycling. The present study shows that palmitoylation of cysteine residues 643 and 644 of the human LHR is a determinant of recycling.

Blotting, Western↗
PubMed1994

The low affinity neurotrophin receptor, p75LNTR, is palmitoylated by thioester formation through cysteine 279.

The low affinity neurotrophin receptor, termed p75LNTR, plays a role in increasing the amount of nerve growth factor that becomes bound to the tyrosine kinase receptor, trkA (Barker, P. A., and Shooter, E. M. (1994) Neuron 13: 203-215), possibly by increasing the nerve growth factor concentration in the microenvironment surrounding the trkA receptor. Because protein acylation may be a means by which cell surface receptor distribution may be regulated, we have determined the acylation status of p75LNTR. We find that p75LNTR expressed in PC12, PCNA, or transfected COS cells is metabolically labeled with [3H]palmitic acid. This modification occurs post-translationally, and the incorporated fatty acid is removed by hydroxylamine treatment at pH 7 or 11 and by sulfhydryl reducing agents, suggesting a thioester linkage to palmitic acid. Consistent with this, p75LNTR in which the juxtamembrane cysteine present at position 279 is substituted with alanine is expressed but cannot be metabolically labeled with [3H]palmitic acid. Substitution of other cysteine residues present in the transmembrane or intracellular domain of the receptor has no effect on protein acylation, suggesting that only Cys279 is esterified to palmitate.

Acylation↗
PubMed1994

X-ray crystallographic structures of adipocyte lipid-binding protein complexed with palmitate and hexadecanesulfonic acid. Properties of cavity binding sites.

Adipocyte lipid-binding protein is a 14.6-kDa polypeptide that is responsible for the intracellular trafficking of fatty acids. Its structure previously has been solved in the apo and holo forms complexed with stearate and oleate. To examine the binding of lipids other than those with a carboxylate headgroup, we have determined the structure of ALBP in complex with a sulfonic acid, hexadecanesulfonic acid, and compared its structure with the natural fatty acid analog, palmitate. Crystallographic refinement led to similar models, both with R-factors of about 20% and a resolution of 1.6 A. results can be compared with earlier studies on C18 fatty acids, both saturated and unsaturated. The previously refined complexes with stearate and oleate in combination with the complexes of palmitate and hexadecanesulfonic acid demonstrate specific positions for water molecules bound in the internal cavity. Many of the water-binding sites are present in both the apo form and the holo forms of the protein. With ligand present, a network of 10 internalized water molecules appear to form a hydrophobic hydration region. In spite of the sp3 geometry of the sulfonic acid derivative, the headgroup occupies the same site as that of the planar carboxylate in natural fatty acids. These results demonstrate that intracellular lipid-binding proteins are capable of binding a wider variety of lipids than previously considered and reveal the importance of interior ordered water molecules in the binding cavity.

Alkanesulfonic Acids↗
PubMed2001

Transcriptional regulation of the Bacillus subtilis bscR-CYP102A3 operon by the BscR repressor and differential induction of cytochrome CYP102A3 expression by oleic acid and palmitate.

The adjacent yrhI and yrhJ genes were identified by the Bacillus subtilis genome sequencing project. We now report that yrhJ (renamed CYP102A3) encodes a cytochrome P450 and that yrhI (renamed bscR) encodes a repressor that negatively regulates the transcription of the bscR-CYP102A3 operon. The transcriptional initiation site of bscR has been mapped by primer extension analysis. An 18-bp perfect palindromic sequence centered 65.5 bp downstream from the transcriptional initiation site of bscR has been identified as the binding site for BscR by gel mobility shift assays. Base substitutions in the 18-bp inverted repeat resulted in derepression of the bscR-xylE transcriptional fusion in vivo. bscR-xylE fusion studies and Northern blot analysis revealed that oleic acid and palmitate could induce the expression of the bscR-CYP102A3 operon to a considerable extent. However, only oleic acid was capable of preventing the binding of BscR to its operator DNA in vitro, suggesting that the induction of CYP102A3 expression by oleic acid and palmitate in B. subtilis might be mediated through different mechanisms.

Amino Acid Sequence↗
PubMedDate not supplied

Amino acid sequence and some ligand binding properties of fatty acid-binding protein from bovine brain.

A fatty acid-binding protein (FABP) from the cytosol of bovine brain was purified by Sephadex G-75 filtration and electrofocusing. The purified protein migrated as a single protein band in 15% polyacrylamide gel electrophoresis with an apparent molecular mass of 14.7 kDa. To ascertain that the purified protein was a FABP, it was submitted to fatty acid-binding tests. Oleic and palmitic acids bound to brain FABP but this was not the case for palmitoyl CoA. By Scatchard analysis the ligand binding values were: Kd = 0.28 microM, Bmax (mol/mol) = 0.6 for oleic acid and Kd = 0.8 microM, Bmax (mol/mol) = 2.1 for palmitic acid. The complete amino acid sequence of the brain FABP was determined and a microheterogeneity was observed. Sequence comparison with other FABPs of known sequence and the observed microheterogeneity demonstrated the presence in brain of several homologous FABPs closely related to heart FABP.

Amino Acid Sequence↗