Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using a primitive Earth evaporating pond model, the synthesis of phosphatidylcholine was accomplished when a reaction mixture of choline chloride and disodium phosphatidate, in the presence of cyanamide and traces of acid, was evaporated and heated at temperatures ranging from 25 degrees to 100 degrees C for 7 hours. Optimum yields of about 15% were obtained at 80 degrees C. Phosphatidylcholine was identified by chromatographic, chemical and enzymatic degradation methods. On enzymatic hydrolysis with phospholipase A2 and phospholipase C, lysophosphatidylcholine and phosphorylcholine were formed, respectively. Alkaline hydrolysis gave glycerophosphorylcholine. The synthesis of phosphatidylcholine as the major compound was accompanied by the formation of lysophosphatidylcholine in smaller amounts. Cyanamide was found to be essential for the formation of phosphatidylcholine, and only traces of HCl, of the order of that required to convert the disodium phosphatidate to free phosphatidic acid were found necessary for the synthesis. This work suggests that phosphatidylcholine, which is an essential component of most biological membranes, could have been synthesized on the primitive Earth.
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PMID:Synthesis of phosphatidylcholine under possible primitive earth conditions. 709 79

The concentration of phospholipids is well suited as indicator for the prognosis of a possibly postnatal respiratory distress syndrome. The method used most frequently up to now has been the determination of the lecithin/sphingomyelin ratio (L/S ratio) by thin layer chromatography. We have developed a specific assay for the quantitative determination of lecithin in amniotic fluid, which yields absolute concentration values and does not require the determination of a concentration ratio. Lecithin is hydrolized by phospholipase C and alkaline phosphatase. Choline is determined afterwards by a highly specific choline kinase from yeast. The total time required is less than 2 h. The usual lecithin concentration present in the 35th to 38th wk of gestation can be determined with a coefficient of variation of 2-3% (n=30). Fetal lung maturity can be expected at a lecithin concentration above 4.7-5.1 mg/100 ml. The method compares well with the L/S ratio. Detailed data about clinical significance will be presented. Good precision accuracy and simple handling make enzymatic lecithin determinations suitable for routine use.
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PMID:A new method of evaluating fetal lung maturity: the enzymatic lecithin determination in amniotic fluid. 711 59

Phosphatidylethanolamine of rat liver microsomes is rapidly methylated by S-adenosyl[methyl-14C]methionine to produce phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine and phosphatidylcholine. Using phospholipase C as a probe, on both opened (0.4% taurocholate or French pressure cell treatment) and unopened microsomes, it is demonstrated that phosphatidylcholine is labelled in the inner leaflet of the bilayer and, to a greater extent, in the outer leaflet. Phosphatidyl-N,N-dimethylethanolamine is labelled in the outer leaflet and in a pool sequestered from phospholipase C in open and closed vesicles. Phosphatidyl-N-monomethylethanolamine is labelled in a similarly sequestered pool. When microsomes containing labelled phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine were incubated with unlabeled S-adenosylmethionine, these phospholipids were methylated to produce phosphatidylcholine in the outer leaflet. This metabolism was inhibited by S-adenosylhomocysteine. Trypsin treatment of unopened microsomes inhibited 95% of the incorporation of 14CH3 into the outer leaflet of the bilayer with no effect on incorporation into sequestered phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine and phosphatidylcholine. Therefore, sequestered phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine are apparently synthesized by enzymes located at the inner surface of the microsomal membranes. These observations suggest that initial methylation of phosphatidylethanolamine takes place at the inner surface of the microsomes and that phosphatidyl-N-monomethylethanolamine is transferred to the outer leaflet to produce phosphatidylcholine. However, phosphatidyl-N-monomethylethanolamine is also methylated at the inner leaflet to produce phosphatidylcholine which does not equilibrate with that of the outer leaflet. Phosphatidylcholine of both the inner and outer bilayer leaflets is uniformly labelled by injection of [14C]methionine, in vivo.
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PMID:Biogenesis of endoplasmic reticulum phosphatidylcholine. Translocation of intermediates across the membrane bilayer during methylation of phosphatidylethanolamine. 721 79

High enriched (50- to 70-fold) fractions of "native" lysosomes were isolated using continuous flow electrophoresis from livers of rats which had not been pretreated with Triton WR-1339. Incubation of lysosomes for 30 min at pH 5.0 in the presence of 5 mM EDTA resulted in a dramatic loss in the content of fatty acids bound to triacylglycerols (137 down to 10 mumol/mg protein) and to phospholipids and an elevation in the level of unesterified fatty acid. Phosphatidylcholine, phosphatidylethanolamine and sphingomyelin concentrations decreased whereas those of lysophosphatidylethanolamine (0.8 up to 8.5% of total lipid-P) and lysophosphatidylcholine (1.9 up to 16.7%) rose in a manner parallel to their respective, fully acylated lipids. Other phospholipids, including phosphatidylinositol, did not change in concentration during incubation. These results indicate that lysosomal phospholipase A, sphingomyelin and triacylglycerol lipase are activated by incubation at acid pH, enabling them to hydrolyze endogenous lysosomal lipids. However, lysosomal phosphatidylinositol-directed phospholipase C is apparently unable to interact with phosphatidylinositol of the lysosomal membrane.
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PMID:Endogenous lipolytic activities during autolysis of highly enriched hepatic lysosomes. 731 38

Fatty acid positional distributions and the fatty acid compositions of diacyl and alkyl acyl analogs of the three major glycerophospholipids of Paramecium tetraurelia were examined. Phosphatidylcholine and the phospho- and phosphonyl ethanolamine glycerolipids were separated into diacyl and alkyl acyl species by thin-layer chromatography after phospholipase C digestion, and acetylation. Phosphatidylcholine and the ethanolamine phosphonolipid were predominantly in the alkyl acyl form and phosphatidylethanolamine was predominantly in the diacyl form. The three major glycerophospholipids were also subjected to hydrolysis by phospholipase A2. Complete and efficient hydrolyses of all three phospholipids were accomplished with the enzyme from porcine pancreas. Sodium tetraborate prevented acyl migration when added to reaction mixtures. Fatty acids released by phospholipase A2 action, and the lysoderivatives were separated by thin-layer chromatography. Fatty acid methyl esters were prepared and analyzed by gas-liquid chromatography. Saturated acids were predominantly at C-1 of diacyl phospholipids. Polyunsaturated fatty acids were mainly at C-2, particularly in the alkyl acyl species. An exception was gamma-linolenate which was a major acid found esterified to C-1 in the three diacyl phospholipids. Identification of this acid at that position supports the idea that in some ciliates there may be an acyltransferase, specific for gamma-linolenate, that esterifies this acid to the glycerophospholipids.
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PMID:Positional distribution of fatty acids in the major glycerophospholipids of Paramecium tetraurelia. 740 Jun 87

The role of rat liver plasma membrane phospholipids in the regulation of protein kinase A, protein kinase C and tyrosine kinase activities was investigated. Plasma membrane composition was modified by phospholipase A2, phospholipase C and phospholipase D treatment and subsequent incorporation of various phospholipids. Phospholipase A2 deactivated the three types of protein kinases, while phospholipase C and D affected the enzymes in a different manner. Phosphatidylcholine and sphingomyelin were found to be the most effective activators of protein kinase A and tyrosine kinase. Incorporation of sphingomyelin and phosphatidylserine into partially delipidated plasma membranes resulted in a significant stimulation of protein kinase C activity. Since sphingomyelin appeared to be a specific effector of the three types of protein kinases under investigation, one might suggest that its role in cellular signaling could be manifested via regulation of protein kinase C as well as via modulation of protein kinase A and tyrosine kinase activities.
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PMID:Role of rat liver plasma membrane phospholipids in regulation of protein kinase activities. 755 80

Phosphatidylcholine (PC) metabolism stimulated by caerulein (Cae), a cholecystokinin analogue, was investigated in rat pancreatic acini prelabeled with [3H]choline or [3H]-myristic acid. Both labels were incorporated mostly into PC. An inhibition of choline incorporation into PC was first observed in response to Cae (100 and 500 pM) stimulation, as indicated by reduced [3H]choline incorporation into trichloroacetic acid-precipitable material. Whereas choline incorporation was reduced in PC, Cae (500 pM) significantly increased [3H]choline metabolites release in the incubation medium. Separation of these metabolites by thin-layer chromatography showed that approximately 90% of the labeled products released into the medium was phosphocholine; however, Cae caused significant increases of [3H]choline release after 5, 15, and 30 min. In response to Cae, manoalide, a phospholipase C (PLC) inhibitor, totally prevented phosphocholine release into the medium but did not affect choline release. Staurosporine, a protein kinase C inhibitor, did not influence basal and Cae-induced choline release. In cells prelabeled with [3H]myristic acid, Cae stimulated within 5 min a rapid increase in intracellular [3H]phosphatidic acid (PA) levels in the presence of the PA phosphohydrolase inhibitor, propranolol; this PA production was further increased after 15 and 30 min of stimulation. The time course of [3H]PA formation in the presence of propranolol was similar to that of choline release in the medium. Staurosporine partially blocked PA accumulation stimulated by Cae after 30 min. In contrast, manoalide significantly reduced basal PA accumulation but did not prevent its production in response to Cae. In the presence of ethanol, Cae also significantly stimulated above control values the formation of [3H]phosphatidylethanol. These data indicate that Cae-induced PC hydrolysis in rat pancreatic acini is mediated mostly by phospholipase D (PLD) to produce PA and choline; they suggest a direct action of Cae on PLD activation, an effect independent of PLC activation.
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PMID:Involvement of phospholipase D in caerulein-induced phosphatidylcholine hydrolysis in rat pancreatic acini. 823 56

The effect of sphingomyelin hydrolysis on triacylglycerol-rich lipoprotein secretion was examined in the human intestinal cell line, CaCo-2. Addition of sphingomyelinase decreased sphingomyelin and phosphatidylethanolamine by 60 and 20%, respectively. Sphingomyelin hydrolysis decreased the basolateral secretion of triacylglycerol mass, newly synthesized triacylglycerol, and apo B mass. Pulse-chase experiments with [35S]methionine demonstrated a decrease in apo B synthesis and a marked decrease in apo B100 and apo B48 secretion without altering apo A1 secretion. Sphingomyelin hydrolysis did not change apo B mRNA levels nor apo B turnover. Phosphatidylcholine-specific phospholipase C did not decrease apo B synthesis or its basolateral secretion. Membrane protein kinase C (PKC) activity was decreased twofold after sphingomyelin hydrolysis. The PKC inhibitor staurosporine decreased apo B mass and newly synthesized apo B secretion. Sphingomyelinase and staurosporine together caused an additional decrease in apo B secretion suggesting that sphingomyelin hydrolysis decreased apo B secretion independently of its effect on PKC activity. Moreover, conditions that increase PKC activity did not increase apo B secretion. Cell-permeable analogs of ceramide decreased immunoreactive apo B secretion. Sphingosine was without effect. The hydrolysis of membrane sphingomyelin by intestinal or pancreatic neutral sphingomyelinase may lead to the accumulation of cellular ceramide, which, in turn, could inhibit triacylglycerol-rich lipoprotein secretion.
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PMID:Release of ceramide after membrane sphingomyelin hydrolysis decreases the basolateral secretion of triacylglycerol and apolipoprotein B in cultured human intestinal cells. 825 18

Phosphatidylcholine, in addition to the widely studied inositol phospholipids is cleaved to produce second messengers in neuronal signal transduction processes. Because of the difficulty in labelling and measuring the metabolism of endogenous phosphatidylcholine in brain tissue, we investigated the utility of measuring the hydrolysis of exogenous labelled substrate incubated with rat cerebral cortical cytosol and membrane fractions as has been successful in studies of phosphoinositide hydrolysis. In the cytosol [3H]phosphatidylcholine was hydrolyzed at a linear rate for 60 min of incubation and GTP gamma S stimulated hydrolysis by 63%. The products of phospholipase C and phospholipase D, phosphorylcholine and choline, contributed only 44% of the [3H]phosphatidylcholine hydrolytic products in the cytosol, with phospholipase D activity slightly predominating. GTP gamma S stimulated cytosolic phospholipase C and reduced phospholipase D activity. [3H]Phosphatidylcholine was hydrolyzed much more slowly by membranes than by cytosol. In membranes the production of [3H]phosphorylcholine and [3H]choline were approximately equal, contributing 27% of the total [3H]phosphatidylcholine hydrolysis, and GTP gamma S only caused a slight stimulation of phospholipase C activity. Chronic lithium treatment (4 weeks) appeared to slightly reduce [3H]phosphatidylcholine metabolism in the cytosol and in membranes, but no statistically significant reductions were achieved. Cytosol and membrane fractions from postmortem human brain metabolized [3H]phosphatidylcholine slowly, and GTP gamma S had no effects. In summary, exogenous [3H]phosphatidylcholine was hydrolyzed by brain cytosol and membranes, and this was stimulated by GTP gamma S, but the complex contributions of multiple metabolic pathways complicates the application of this method for studying individual pathways, such as phospholipase D which contributes only a fraction of the total processes hydrolyzing exogenous [3H]phosphatidylcholine.
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PMID:Hydrolysis of exogenous [3H]phosphatidylcholine by brain membranes and cytosol. 827 95

These experiments were designed to study signal transduction pathways in alveolar macrophages stimulated by condensed tannin or zymosan. Condensed tannins, present in cotton mill dust, alter the host-defense function of alveolar macrophages and may contribute to the pathogenesis of byssinosis. We tried to determine the early steps in signal transduction mechanisms of cell activation by tannin. With the quantification of 51Cr release, we determined that tannin was cytotoxic for the cells after 30 min activation with 130 micrograms for 2 x 10(6) cells. 51Cr release was similar for control cells and zymosan- or 30 micrograms tannin-activated cells. Using the luciferine luciferase reaction, we showed that tannin markedly depleted ATP cell content. In inositol-labeled cells, tannin increased inositolphosphate release in a dose-dependent manner. In lysoPAF-labeled cells, tannin induced synthesis of phosphatidic acid and diglycerides. In the presence of ethanol, the level of tannin-induced phosphatidic acid was slightly reduced, and phosphatidylethanol was synthesized. No phosphatidylethanol was found in alveolar macrophages stimulated by zymosan in the presence of ethanol. GF 109203X, a specific inhibitor of protein kinase C decreased only tannin-induced phosphatidylethanol synthesis. In conclusion, tannin (at 30 or 130 micrograms/ml) activated an inositol phospholipase C in alveolar membranes. Phosphatidylcholine phospholipases C and D were found only at the higher concentration of tannin.
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PMID:Distinct signal transduction pathways for activation of rabbit alveolar macrophages in vitro by cotton bract tannin. 865 14


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