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PubMed1975

Effect of inhibition of protein synthesis on lipid metabolism in Lactobacillus plantarum.

In Lactobacillus plantarum 17-5, lipid synthesis appears to be correlated with protein synthesis. Inhibition of protein synthesis by chloramphenicol (50 mug/ml) caused the nearly simultaneous inhibition of incorporation of radioactive oleic acid into polar lipids before the cessation of growth. In addition, de novo fatty acid synthesis, as determined by the incorporation of radioactive acetate into cellular lipids, was also inhibited. Removal of the antibiotic resulted in the resumption of growth, protein synthesis, and polar lipid synthesis. Inhibition of protein synthesis by leucine deprivation also produced a marked reduction in the incorporation of radioactive oleic acid into the total polar lipids at about the same time that growth stopped (30 to 60 min after the removal of leucine). However, the different classes of lipids behaved differently. For example, the incorporation of oleic acid into cardiolipin was inhibited immediately upon removal of leucine from the cultures, whereas incorporation into phosphatidyl-glycerol was maintained at near normal rates for 60 min after the removal of leucine and then ceased. In contrast, the accumulation of radioactive oleic acid in a neutral lipid identified as diglyceride occurred to a much greater extent in leucine-deprived cultures than in control (+ leucine) cultures. Upon addition of leucine to leucine-deprived cultures, the rates of synthesis of phosphatidyl-glycerol and cardiolipin returned to normal; the amount of radioactivity in the diglyceride fraction decreased to normal levels concomitantly with increased phospholipid synthesis.

Bacterial Proteins↗

PubMed1976

Biosynthesis and assembly of envelope lipoprotein in a glycerol-requiring mutant of Salmonella typhimurium.

A glycerol-requiring mutant of Salmonella typhimurium was used in a study of the biosynthesis and assembly of a structural lipoprotein in the cell envelope of gram-negative bacteria. Upon removal of glycerol from the growth medium, the biosynthesis of lipoprotein, as measured by radioactive arginine incorporation, was reduced by the same extent as that of other envelope proteins, the cumulative incorporation of arginine being 20% of that of the unstarved control cells. However, the incorporation of radioactive palmitate into lipoprotein was more severely curtailed after glycerol starvation, the cumulative rate of which was 8% of that observed in the unstarved cells. It was further observed that the lipoprotein synthesized in the glycerol-starved cells was more enriched in unmodified cysteine, which is known to be the N-terminal amino acid of lipoprotein, than that synthesized in the unstarved cells. We conclude that the synthesis of the apoprotein portion of Braun's lipoprotein proceeds independently of the attachment of diglyceride to the sulfhydryl group of the N-terminal cysteine and may, in fact, precede the incorporation of the diglyceride moiety.

Amino Acids↗

PubMed1976

Membrane lipoteichoic acid of Streptococcus pyogenes and its stabilized L-form and the effect of two antibiotics upon its cellular content.

Membrane lipoteichoic acid continues to be synthesized by an osmotically fragile, stabilized L-form of Streptococcus pyogenes. Chromatographic and electrophoretic comparisons indicate that the lipid componenent of lipoteichoic acid in this L-form and its parental streptococcus is glycerophosphoryldiglucosyl diglyceride and not phosphatidylkojibiosyl diglyceride. Based upon dry weight determinations, the yield of lipoteichoic acid from the L-form is 0.19%, as compared with 0.97% from the streptococcus. When grown with bacitracin the L-form contains the same amount of teichoic acid as when grown without this antibiotic; however, its lipoteichoic acid content is reduced by 85%. Similarly, the L-form grown with novobiocin for 10 h contains only 17% of the teichoic acid found in control cells.

Bacitracin↗

PubMed1977

Phenethyl alcohol inhibition of sn-glycerol 3-phosphate acylation in Escherichia coli.

In vivo and in vitro experiments were performed to determine how phenethyl alcohol (PEA) inhibits phospholipid synthesis in Escherichia coli. This drug drastically reduced the rate of incorporation of sn-glycerol 3-phosphate into the phospholipids of an sn-glycerol 3-phosphate auxotroph. PEA also reduced the rate of fatty acid incorporation into the phospholipids of a fatty acid auxotroph. The kinetics of PEA inhibition of the rate of incorporation of sn-glycerol 3-phosphate were almost identical to those of PEA inhibition of the rate of fatty acid incorporation into phospholipids. The in vivo experiments suggested that the rate-limiting step(s) in phospholipid biosynthesis inhibited by PEA is at the level of the acylation of sn-glycerol 3-phosphate or beyond this step. PEA inhibited the sn-glycerol 3-phosphate acyltransferase with either palmitoyl coenzyme A or palmitoyl-acyl carrier protein as the acyl donor. This drug, however, had no effect on the cytidine 5'-diphosphate-diglyceride:glycerol 3-phosphate phosphatidyl transferase, cytidine 5'-diphosphate-diglyceride:L-serine phosphatidyl transferase, and acyl coenzyme A:lysophatidic acid acyltransferase. The in vitro findings suggested that PEA inhibits phospholipid synthesis primarily at the level of sn-glycerol 3-phosphate acyltransferase.

Acylation↗

PubMed1977

Membrane lipid biosynthesis in Acholeplasma laidlawii B: incorporation of exogenous fatty acids into membrane glyco- and phospholipids by growing cells.

The extent of incorporation of a wide variety of exogenous saturated, unsaturated, branched-chain, and cyclopropane fatty acids into the membrane lipids of Acholeplasma laidlawii B was systematically studied. Within each fatty acid class the extent of incorporation generally increased markedly with increasing chain length, reached a maximum, and then declined progressively but less sharply with further increases above that chain length giving maximal direct incorporation. Certain shorter-chain members of each fatty acid class underwent complete or partial conversion to longer-chain homologues before utilization for complex lipid biosynthesis. The degree and extent of chain elongation and direct incorporation and the characteristic dependence of each of these processes on fatty acid chain length and structure correlated well with the physical properties (melting temperatures) of the exogenous fatty acids. The in vivo specificity of the enzyme systems responsible for the incorporation of exogenous fatty acids was such that the fluidity and physical state of the membrane lipids were maintained within a definite, albeit a relatively wide, range. We also observed that the neutral glycolipids typically have similar fatty acid compositions, which are somewhat different from those of the major phosphatides, which also exhibit similar fatty acid spectra. The phosphorylated glycolipid glycerophosphoryldiglucosyl diglyceride, however, always maintained a unique fatty acid composition quite different from that of the diglucosyl diglyceride from which it is presumably derived. These characteristic differences in fatty acid composition appear to function to minimize differences in phase transition temperatures, thus producing a more physicochemically homogeneous mixture of membrane lipids than would result from a nonspecific incorporation of fatty acids.

Acholeplasma laidlawii↗

PubMed1979

Biosynthesis of phospholipids in Bacillus megaterium.

Information on the biosynthesis of phospholipids in bacteria has been derived principally from the study of Escherichia coli and other gram-negative organisms. We have now carried out a detailed study of the pathways of phospholipid biosynthesis in the gram-positive organism Bacillus megarterium KM in relation to investigations on the biogenesis of lipid asymmetry in membranes. Radioactive precursors such as 32Pi and [3H]palmitate initially label phosphatidylethanolamine much more than phosphatidylglycerol. This raised the possibility that phosphatidylglycerol may be the precursor of phosphatidylethanolamine in a pathway different from that in E. coli. Phosphatidylglycerol is known to be highly reactive metabolically, since it functions as a donor of phosphatidyl residues in the synthesis of cardiolipin and as a donor of glycerophosphate residues in the synthesis of teichoic acids and of membrane-derived oligosaccharides. The large pool of phosphatidylglycerol would dilute the radioactive isotope, slowing the initial rate of incorporation of label into phosphatidylethanolamine. However, assays of cell-free extracts revealed no evidence for such a novel pathway. Instead, phosphatidylserine synthase (cytidine 5'-diphosphate-diglyceride:L-serine phosphatidyl transferase) and phosphatidylserine decarboxylase were detected, although at low levels. These results suggest that the pathway in B. megaterium is the same as that in E. coli in which phosphatidylserine, derived from cytidine 5'-diphosphate-diglyceride, is the precursor of phosphatidylethanolamine. The lag in the appearance of label in phosphatidylethanolamine appears to be the effect of a considerable pool of phosphatidylserine (ca. 5 to 10% of the total phospholipid) in certain strains of B. megaterium. The lag in labeling can be correlated with the size of the pool of phosphatidylserine. Pulse-chase experiments in vivo support the conclusion that in B. megaterium phosphatidylserine is not derived from phosphatidylglycerol. Rates of turnover of the membrane phospholipids of B. megaterium have also been studied.

Bacillus megaterium↗

PubMed1980

Two distinct pools of membrane phosphatidylglycerol in Bacillus megaterium.

The predominant membrane lipid in Bacillus megaterium ATCC 14581, phosphatidylglycerol (PG), is present in two distinct pools, as shown by [32P]phosphate incorporation and chase experiments. One pool (PGt) undergoes rapid turnover of the phosphate moiety, whereas the second pool (PGs) exhibits metabolic stability in this group. The phosphate moiety of the other major phospholipid, phosphatidylethanolamine, is stable to turnover. [32P]phosphate- and [2-3H]glycerol-equilibrated cultures yielded the following glycerolipid composition: 56 mol% PG (34 mol% PGt and 22 mol% PGs), 21 mol% phosphatidylethanolamine, 1 to 2 mol% phosphatidylserine, 20 mol% diglycerides, less than 0.5 mol% cardiolipin, and 0.2 to 0.4 mol% lysophosphatidylglycerol. Accumulation of PG was halted immediately after the addition of cerulenin, an inhibitor of de novo fatty acid synthesis, whereas phosphatidylethanolamine accumulation continued at the expense of the diglyceride and PG pools. Strikingly, initial rates of [32P]phosphate incorporation into PG were unaffected by cerulenin. In control cultures at 35 degrees C, incorporation of [32P]phosphate into PG exhibited a biphasic time course, whereas incorporation into phosphatidylethanolamine was concave upward and lagged behind that of PG during the initial rapid phase of PG incorporation. Finally, levels of lysophosphatidylglycerol expanded rapidly after cerulenin addition at 20 degrees C, but not at 35 degrees C. Moreover, incorporation of [32P]phosphate into lysophosphatidylglycerol lagged behind incorporation into PG in both the presence and absence of cerulenin at 20 and 35 degrees C.

Bacillus megaterium↗

PubMed1967

Isolation and characterization of glycolipids from some photosynthetic bacteria.

Glycosyl glycerides have been found in substantial amounts in Chloropseudomonas ethylicum but could not be detected in two strains of Rhodopseudomonas palustris. Rhodospirillum molischianum possibly contains small amounts of monoglycosyl diglyceride. The glycolipids of C. ethylicum have been separated into two components. One of these, glycolipid I, is a monogalactosyl diglyceride. Glycolipid II, upon acid hydrolysis, yields galactose, rhamnose, and a third, unidentified sugar. The glycolipids or total lipids of the photosynthetic bacteria examined contained saturated and monounsaturated, but none of the more highly unsaturated, fatty acids.

Bacteria↗

PubMed1969

Separation and identification of the polar lipids of Chromatium strain D.

The polar lipids of the autotrophically grown, obligately anaerobic, photosynthetic bacterium Chromatium strain D were separated by paper chromatography. Four major phospholipids were identified: lysophosphatidylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. In addition, three glycolipids were observed and characterized, namely, monoglucosyldiglyceride, which is found in other biological systems, and (mannosyl, glucosyl)-diglyceride and (dimannosyl, glucosyl)-diglyceride, which heretofore have not been observed in nature.

Autoradiography↗

PubMed1994

Evidence that v-Src-induced phospholipase D activity is mediated by a G protein.

v-Src-induced increases in diglyceride are derived from phosphatidylcholine via a type D phospholipase (PLD) and a phosphatidic acid phosphatase. v-Src-induced PLD activity, as measured by PLD-catalyzed transphosphatidylation of phosphatidylcholine to phosphatidylethanol, is inhibited by GDP beta S, which inhibits G-protein-mediated intracellular signals. Similarly, v-Src-induced increases in diglyceride are also blocked by GDP beta S. In contrast to the PLD activity induced by v-Src, PLD activity induced by the protein kinase C agonist, 12-O-tetradecanoylphorbol-13-acetate (TPA), was insensitive to GDP beta S. Consistent with the involvement of a G protein in the activation of PLD activity by v-Src, GTP gamma S, a nonhydrolyzable analog of GTP that potentiates G-protein-mediated signals, strongly enhanced PLD activity in v-Src-transformed cells relative to that in parental BALB/c 3T3 cells. The effect of GTP gamma S on PLD activity in v-Src-transformed cells was observed only when cells were prelabeled with [3H]myristate, which is incorporated exclusively into phosphatidylcholine, the substrate for the v-Src-induced PLD. There was no difference in the effect of GTP gamma S-induced PLD activity on v-Src-transformed and BALB/c 3T3 cells when the cells were prelabeled with [3H]arachidonate, which is not incorporated into phospholipids that are substrates for the v-Src-induced PLD. Similarly, GDP beta S inhibited PLD activity in v-Src-transformed cells much more strongly than in BALB/c 3T3 cells when [3H]myristate was used to prelabel the cells. The GTP-dependent activation of PLD by v-Src was dependent upon the presence of ATP but was unaffected by either cholera or pertussis toxin. These data suggest that v-Src induces PLD activity through a phosphorylation event and is mediated by a cholera and pertussis toxin-insensitive G protein.

3T3 Cells↗

PubMed1985

Lipid profiles of Aspergillus niger and its unsaturated fatty acid auxotroph, UFA2.

A comparative study of the mycelial lipid composition of a wild strain (V35) and one unsaturated fatty acid auxotroph (UFA2) of Aspergillus niger has been performed. The lipid composition of both strains are qualitatively the same but quantitatively different. All the strains contain the following phospholipids: cardiolipin, phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylcholine, and phosphatidylserine; and triglycerides, diglycerides, monoglycerides, ergosterol, and sterol esters as the neutral lipids; mono- and di-galactosyl diglyceride as the major glycolipids along with small amounts of the corresponding mannose analogs. Phosphatidylethanolamine and phosphatidylcholine constitute the bulk of the phospholipids. The mutant (UFA2) contains a higher level of glycerides and lower levels of sterol (both free and esterified form), phospholipids, and glycolipids than the wild type. Aspergillus niger contains C16 to C18 saturated and unsaturated fatty acids. Small amounts of long-chain (C20 to C24) and short-chain (C10 to C14) saturated and unsaturated acids are also present. Linoleic, oleic, and palmitic are the major acids, stearic and linolenic acids being minor ones. UFA2 grows only in the presence of unsaturated fatty acid (C16 or C18) and accumulates a higher concentration of supplemented acid which influences its fatty acid profile.

Aspergillus niger↗

PubMed1985

Cone-shaped lipids increase the susceptibility of phospholipids in bilayers to the action of phospholipases.

Addition of cardiolipin or diacylglycerol to dispersions of phosphatidylcholine greatly increased hydrolysis by snake venom or pancreatic phospholipase A2, as well as by a microbial phospholipase. Monogalactosyl diglyceride which, like cardiolipin and diacylglycerol, will form nonbilayer hexagonal II structures also caused an increase in the breakdown of phosphatidylcholine. Addition of digalactosyl diglyceride, a bilayer lipid from the same source, had a much smaller effect on the three phospholipases, indicating that stimulation by the nonbilayer lipids was not due to their fatty acid compositions. Stimulation of the microbial phospholipase by cardiolipin did not require the presence of calcium, leading to the conclusion that the formation of nonbilayer structures was not necessary. The results suggest that cone-shaped lipids increase the accessibility of lipids in bilayers to phospholipases by decreasing the packing of the polar head groups.

Animals↗

PubMed1982

5-HT-stimulated arachidonic acid release from labeled phosphatidylinositol in blowfly salivary glands.

In blowfly salivary glands, breakdown of phosphatidylinositol has been linked to the activation of hormone-sensitive Ca2+ channels. Addition of 5-hydroxytryptamine to blowfly salivary glands stimulated the breakdown of phosphatidylinositol prelabeled with 32P or [3H]arachidonic acid. This was associated with a transient accumulation of [3H]arachidonic-labeled diglyceride. There was no appreciable effect of 5-hydroxytryptamine on breakdown of phosphatidylethanolamine or phosphatidylcholine labeled with 32P or [3H]arachidonic acid, indicating that phosphatidylinositol was the immediate source of diglyceride. Extracellular Ca2+ was necessary for [3H]arachidonic acid but not 32P loss from phosphatidylinositol. Addition of arachidonic acid to salivary glands did not stimulate salivary gland secretion or 45Ca flux. In contrast, 5-hydroxytryptamine stimulated both salivary gland secretion and 45Ca flux. These results indicate that, although [3H]arachidonic acid is incorporated into phosphatidylinositol and its release from this phospholipid is increased by 5-hydroxytryptamine, the liberated arachidonic acid does not stimulate salivary gland secretion or 45Ca flux.

Animals↗

PubMed1976

Intramicrosomal location in intestine of enzymes which synthesize complex lipid.

Smooth and rough microsomal fractions were prepared from hamster intestinal mucosa and assayed for RNA, diglyceride acyltransferase, cholinephosphotransferase and lysolecithin acyltransferase. The specific activity of cholinephosphotransferase was 4-fold more in the rough than in the smooth microsomal fractions, whereas diglyceride and lysolecithin acyltransferases were respectively 26 and 57% more active in the rough microsomal fraction. The two acyltransferases were similarly located in the microsomes and more closely corresponded to the location of dietary lipid than cholinephosphotransferase.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1996

Responses of oral epithelial cells to dental resin components.

The light-polymerized resins used in dentistry and their various constituents have been shown to produce significant levels of cytotoxicity, depending upon the material and the cell type exposed to it. These responses include altered cell growth and macromolecule synthesis. The current study examined the effects of several resin components on growth and lipid metabolism of oral epithelial cells. Resin discs were fabricated from triethyleneglycol dimethacrylate (TEGDMA) as received from the manufacturer and after removal of the stabilizer methyl ether hydroquinone (MEHQ). Some discs also contained the initiators benzoyl peroxide (BPO) and camphoroquinone (CQ), and/or an activator, dimethylaminoethyl methacrylate (DMAEMA). After polymerization, the ability of components to elute from the discs and alter cell growth and lipid synthesis were assayed by a colorimetric method and thin layer chromatography respectively. Purified TEGDMA had little effect on the cells' growth or lipid metabolism, while TEGDMA containing MEHQ did inhibit growth as well as total polar lipid synthesis. Eluates from discs containing DMAEMA inhibited cell growth as well as decreasing polar lipid formation. However, this same material produced increased synthesis of diglycerides and cholesterol esters. Eluates from BPO-containing discs, as well as those with CQ, with or without DMAEMA resulted in increased levels of diglycerides. These results demonstrate that even after polymerization, components used in dental resins may elute into the immediate environment and alter various cell metabolic processes.

Animals↗

PubMed1990

The conductance of cultured epithelial cell monolayers: oxidants, adenosine triphosphate, and phorbol dibutyrate.

Oxidants are one class of inflammatory molecules that may contribute to an increase in epithelial permeability to water and solutes that commonly occurs during acute inflammation. We and others have observed that oxidants reversibly alter the paracellular conductance of Madin Darby canine kidney epithelial (MDCK) cell monolayers. The mechanism by which oxidants reversibly alter MDCK monolayer conductance is not yet fully understood. Some investigators have suggested that oxidants might alter MDCK monolayer paracellular conductance by depleting adenosine triphosphate (ATP) in the cells. When we exposed MDCK cells to doses of oxidants that increased monolayer paracellular conductance in earlier studies, ATP was depleted within 10 min. However, when ATP was depleted to similar levels with an inhibitor of glycolytic ATP production, 2-deoxy-D-glucose (DOG), monolayer paracellular conductance was not increased. Severe ATP depletion with DOG and the mitochondrial metabolic inhibitor, antimycin A (AA), had very limited, ATP-independent effects on paracellular conductance. As an alternative explanation for the effects of oxidants on MDCK monolayer paracellular conductance, we had reported that oxidants increased production of inositol phosphates and diglycerides in MDCK cells. Synthetic diglyceride and phorbol dibutyrate (PDBU) increased MDCK monolayer conductance to ions and mannitol in earlier studies. When MDCK cell ATP was depleted with DOG (to the level caused by oxidants), the increase in conductance following PDBU was not different from that observed in control cells. More severe ATP depletion, with DOG and AA, prevented the increase in conductance following PDBU.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1982

Gastric lipase in the newborn rat.

A substantial portion of rat milk triglycerides was hydrolyzed in the ligated stomach of suckling rats with excised lingual gland and pancreas, due to the action of gastric lipase. Free fatty acids were the main lipolytic products. There were some diglycerides and traces of monoglycerides. Medium chain length (C8-C12) fatty acids were predominantly recovered in the free fatty acid fraction, whereas the remaining tri- and diglycerides became richer in long chain (greater than or equal to C14) fatty acids suggesting a preferential lipolysis of medium chain fatty acid ester bonds. The lipase activity in extracts of stomach wall and sublingual gland tissue was more stable at acid pH and more resistant to the action of pepsin than the activity of pancreatic lipase. Trypsin strongly affected lingual lipase activity but only moderately reduced gastric and pancreatic lipase activity. Presence of sodium taurocholate made the lingual and gastric lipases less sensitive to proteolytic attack. It was also found that the activity of gastric lipase, related to the tissue protein content, decreased with the age of rats, whereas that of lingual lipase increased. The joint capacity of the stomach and lingual gland lipases amounted to about 50% of the total digestive lipolytic capacity 6 days after rat birth but decreased to about 20% at 60 days of life. This was due mainly to the considerable increase in the pancreatic gland size.

Age Factors↗

PubMed2006

Estrogen modulation of MgATPase activity of nonmuscle myosin-II-B filaments.

The study tested the hypothesis that estrogen controls epithelial paracellular resistance through modulation of myosin. The objective was to understand how estrogen modulates nonmuscle myosin-II-B (NMM-II-B), the main component of the cortical actomyosin in human epithelial cervical cells. Experiments used human cervical epithelial cells CaSki as a model, and end points were NMM-II-B phosphorylation, filamentation, and MgATPase activity. The results were as follows: 1) treatment with estrogen increased phosphorylation and MgATPase activity and decreased NMM-II-B filamentation; 2) estrogen effects could be blocked by antisense nucleotides for the estrogen receptor-alpha and by ICI-182,780, tamoxifen, and the casein kinase-II (CK2) inhibitor, 5,6-dichloro-1-beta-(D)-ribofuranosylbenzimidazole and attenuated by AG1478 and PD98059 (inhibitors of epithelial growth factor receptor and ERK/MAPK) but not staurosporine [blocker of protein kinase C (PKC)]; 3) treatments with the PKC activator sn-1,2-dioctanoyl diglyceride induced biphasic effect on NMM-II-B MgATPase activity: an increase at 1 nm to 1 microM and a decrease in activity at more than 1 microM; 4) sn-1,2-dioctanoyl diglyceride also decreased NMM-II-B filamentation in a monophasic and saturable dose dependence (EC(50) 1-10 microM); 5) when coincubated directly with purified NMM-II-B filaments, both CK2 and PKC decreased filamentation and increased MgATPase activity; 6) assays done on disassembled NMM-II-B filaments showed MgATPase activity in filaments obtained from estrogen-treated cells but not estrogen-depleted cells; and 7) incubations in vitro with CK2, but not PKC, facilitated MgATPase activity, even in disassembled NMM-II-B filaments. The results suggest that estrogen, in an effect mediated by estrogen receptor-alpha and CK2 and involving the epithelial growth factor receptor and ERK/MAPK cascades, increases NMM-II-B MgATPase activity independent of NMM-II-B filamentation status.

Biological Transport↗