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)

It is widely accepted that insulin action does not involve inositol phospholipid hydrolysis through the stimulation of a phosphatidylinositol-specific phospholipase C (PI-PLC). This consideration prompted us to investigate the insulin effect on the mechanism leading to the accumulation of diacylglycerol (DAG) and phosphatidic acid (PA) in rat hepatocytes. Basically, insulin induces: (i) a significant increase of both [3H]glycerol and fatty acid labelling of DAG; (ii) a significant increase of PA labelling preceding DAG labelling and paralleled by a decrease of phosphatidylcholine (PC) labelling. These observations, which suggest an insulin-dependent involvement of a phospholipase D, are strengthened by the increase of PC-derived phosphatidylethanol in presence of ethanol. Finally, the observation that the PA levels do not return to basal suggests that other mechanisms different from PC hydrolysis, such as the stimulation of direct synthesis of PA, may be activated.
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PMID:Insulin effect on isolated rat hepatocytes: diacylglycerol-phosphatidic acid interrelationship. 142 Mar 24

The properties of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis were studied in detail. The enzyme was extremely thermostable in 0.1% bovine serum albumin and retained 73% of its activity at 100 degrees C for 10 min, while it was labile in the absence of albumin. The enzymatic activity was inhibited by HgCl2 or p-chloromercuriphenylsulfonic acid and restored by dithiothreitol. The kinetic parameters (Km and Vmax) of PI-PLC were determined for the mixed micelle of yeast phosphatidylinositol (PI)/Triton X-100 or sodium deoxycholate. Four PIs having different acyl chains: dilauroylphosphatidylinositol (DLPI), dimyristoylphosphatidylinositol (DMPI), dipalmitoylphosphatidylinositol (DPPI) and dioleoylphosphatidylinositol (DOPI) were synthesized from yeast PI through the processes of deacylation and reacylation, identified by infrared (IR) and Fourier transform nuclear magnetic resonance (FT-NMR) spectra, and subjected to the action of PI-PLC. All the synthetic PIs were hydrolyzed by this enzyme, with DLPI and DMPI being the best substrates. PI-PLC did not catalyze the hydrolysis of the phosphatidylnucleosides 5'-phosphatidylcytidine, 5'-phosphatidyluridine, 5'-phosphatidylthymidine, 5'-phosphatidyladenosine and 5'-phosphatidyl-2'-deoxyadenosine.
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PMID:The study on phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis: synthesis of homogeneous substrates, substrate specificity and other properties. 142 68

We have studied four strains of Tetrahymena thermophila, each of which expresses a different allele of the SerH gene and produces a distinctive surface protein of the immobilization antigen (i-antigen) class. Following exposure of the strains to [3H]ethanolamine or [3H]myristic acid, a protein corresponding in molecular mass to the characteristic i-antigen for that strain became highly labeled, as determined by mobility in sodium dodecylsulfate-polyacrylamide electrophoresis gels. Furthermore, antibodies raised to the i-antigens of the T. thermophila strains selectively immunoprecipitated radioactive proteins having molecular mass identical to that of the i-antigen characteristic for that particular strain. The lipid moieties labeled by [3H]myristate were not susceptible to hydrolysis by exogenous phosphatidylinositol-specific phospholipase C from bacteria. However, when protein extraction was carried out in the absence of phospholipase C inhibitors, radioactive fatty acids derived from [3H]myristate were rapidly cleaved from the putative i-antigens. On the basis of available data, it was concluded that T. thermophila i-antigens contain covalently-linked glycosyl-phosphatidylinositol anchors.
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PMID:Immobilization antigens from Tetrahymena thermophila are glycosyl-phosphatidylinositol-linked proteins. 145 61

Both salt-soluble and detergent-soluble rat brain globular acetylcholinesterases (SS- and DS- AChE EC 3.1.1.7) are amphiphiles, as shown by detergent dependency of enzymatic activity and binding to liposomes. Proteinase K and papain treatment transformed SS-AChE and DS-AChE into forms that, in absence of detergent, no longer aggregated nor bound to liposomes. In contrast, phosphatidylinositol-specific phospholipase C had no effect on these properties. Labeling DS-AChE with 3-(trifluoromethyl)-3-(m-(125I)-iodophenyl) diazirine ([125I]TID) revealed, by polyacrylamide gel electrophoresis under reducing conditions, one single band of 69 kD apparent molecular mass. The same pattern was previously obtained with Bolton and Hunter reagent-labeled enzyme. Proteinase K treatment transformed the 11 S [125I]TID labeled AChE into a 4 S form which no longer showed 125I-radioactivity and was unable to bind to liposomes. These results are compatible with the existence of a hydrophobic segment present both on salt-soluble and detergent-soluble 11 S AChE as well as on the minor forms 4 S and 7 S. This segment is not linked to the catalytic subunits by disulfide bounds in contrast to the 20 kD non-catalytic subunit described by Inestrosa et al.
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PMID:A unique hydrophobic domain of rat brain globular acetylcholinesterase for binding to cell membranes. 146 72

An acidic glycoconjugate could be extracted from a delipidated residue fraction of [3H]galactose, [3H]mannose or [32P]orthophosphate metabolically labeled Entamoeba histolytica with water/ethanol/diethylether/pyridine/NH4OH (15:15:5:1:0.017). The radioactively labeled glycoconjugate comprised 50-55% of the total [3H]galactose label incorporated into macromolecules. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the radiolabeled glycoconjugate showed two diffuse smears centering around 110 kDa and 45 kDa. Similar profiles were observed for both [3H]galactose- and [32P]orthophosphate-labeled glycoconjugate. No such bands were visible in [35S]methionine-labeled material. The hydrophobic nature of this glycoconjugate was inferred from its chromatographic behavior on phenyl-Sepharose. The molecule was rendered hydrophilic after digestion with phosphatidylinositol-specific phospholipase C. It was also sensitive to deamination by nitrous acid. Mild acid hydrolysis led to its fragmentation into smaller molecules as revealed by Sepharose 4B chromatography. Paper chromatographic analysis of the depolymerized [3H]galactose- and [3H]mannose-labeled fragments revealed that each was sensitive to alkaline phosphatase. The major dephosphorylated fragment migrated as an apparent galactose and mannose containing disaccharide which migrated identically to the Gal beta 1-4Man disaccharide derived from the lipophosphoglycan of Leishmania donovani. The above data support the existence of a major acidic glycoconjugate in E. histolytica bearing striking structural similarities to the lipophosphoglycan of Leishmania.
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PMID:Identification and partial characterization of a lipophosphoglycan from a pathogenic strain of Entamoeba histolytica. 147 94

The present report describes the radioactive labeling of polar lipids in in vitro cultures of Plasmodium falciparum as well as their extraction with organic solvents and their partial characterization by chemical and enzymatic methods. All substances detected could be cleaved by alkali, suggesting that they were esters rather than sphingolipids or compounds containing alkyl groups. Dolichol-cycle intermediates were not detected. Phosphatidylinositol, phosphatidylethanolamine, and phosphatidylcholine were labeled by fatty acids and inositol or ethanolamine, respectively, confirming their de novo synthesis by the parasite. Metabolic labeling with glucosamine and cleavage by phosphatidylinositol-specific phospholipase C provided evidence of the formation of N-acetyl-glucosaminyl-phosphatidylinositol, an obligate precursor in the biosynthesis of glycosylphosphatidylinositol membrane anchors of proteins.
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PMID:Labeling and initial characterization of polar lipids in cultures of Plasmodium falciparum. 149 20

Trypanosoma cruzi enters host cells via formation of an acidic vacuole which is subsequently disrupted, allowing the parasite access to the cytoplasm. We show that in an acid environment, release of the parasite surface neuraminidase is enhanced, and this release is likely mediated by a phosphatidylinositol-specific phospholipase C (PIPLC), since antibodies to a carbohydrate epitope (CRD) revealed in glycosylphosphatidylinositol (GPI)-anchored proteins after PIPLC cleavage remove the great majority of the soluble neuraminidase activity from culture supernatants. The neuraminidase is active at acidic pH, and is capable of desialylating known vacuolar constituents, i.e., lysosomal membrane glycoproteins. Parasite escape into the cytoplasm is significantly facilitated in terminal sialylation-defective mutant Lec 2 cells, and enzymatically desialylated membranes are more susceptible to lysis by a parasite hemolysin previously implicated in vacuole membrane rupture. These findings provide evidence that terminal sialylation on carbohydrate moieties contributes to maintaining lysosomal membrane integrity, and indicate a role for a protozoan-derived neuraminidase in facilitating parasite entry into host cells. These observations raise the possibility that other microbial neuraminidases may serve a similar function in acidic intracellular compartments.
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PMID:Desialylation of lysosomal membrane glycoproteins by Trypanosoma cruzi: a role for the surface neuraminidase in facilitating parasite entry into the host cell cytoplasm. 150 Aug 49

Human monocytic leukemic cell line THP-1 was incubated with transforming growth factor-beta 1 (TGF-beta 1) and retinoic acid (RA) and the expression of Fc gamma RIII was investigated. Fc gamma RIII was induced after incubation of the cells with both TGF-beta 1 and RA but not with either TGF-beta 1 or RA alone. Such effects of TGF-beta 1 and RA were not detected on human promyelocytic HL-60 cells. Northern blot analysis revealed the induction of Fc gamma RIII transcripts in THP-1 cells. Furthermore, the Fc gamma RIIIs newly expressed on the cell surface were cleaved by phosphatidylinositol-specific phospholipase C (PI-PLC) and reacted with monoclonal antibody MG38 which specifically binds to granulocyte-type Fc gamma receptors. These results indicated that TGF-beta 1 could induce phosphatidylinositol-glycan-linked Fc gamma RIII (Fc gamma RIII-I) in THP-1 cells in the presence of RA.
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PMID:Induction of phosphatidylinositol-glycan-linked Fc gamma RIII in human monocytic THP-1 cells by transforming growth factor-beta 1 and retinoic acid. 153 73

Sarcolemmal membrane vesicle preparations from white and red muscles of rat were found to contain a carbonic anhydrase which was indistinguishable from carbonic anhydrase IV from rat lung. This isozyme appears to account for all of the carbonic anhydrase activity in the sarcolemmal vesicle preparations. Digestion of 39-kDa CA IV with endoglycosidase F reduced the Mr to 36 kDa, suggesting that it contains one N-linked oligosaccharide. Treatment of sarcolemmal vesicles with phosphatidylinositol-specific phospholipase C released all of the activity, indicating that the enzyme is anchored to membranes by a phosphatidylinositol-glycan linkage. White muscle sarcoplasmic reticulum vesicles also contain a small amount of 39-kDa CA IV-type enzyme. A 52-kDa polypeptide in sarcoplasmic reticulum membranes cross-reacts with anti-human CA II and anti-rat CA II antisera, but does not bind to the sulfonamide affinity column. This cross-reacting polypeptide has no detectable CA activity.
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PMID:Rat skeletal muscle membrane associated carbonic anhydrase is 39-kDa, glycosylated, GPI-anchored CA IV. 153 9

The glycosylphosphatidylinositol (GPI)-anchor of the plasma membrane-associated heparan sulfate (HS) proteoglycan was metabolically radiolabeled with [3H]myristic acid, [3H]palmitic acid, [3H]inositol, [3H]ethanolamine, or [32P]phosphate in rat ovarian granulosa cell culture. Cell cultures labeled with [3H]myristic acid or [3H]palmitic acid were extracted with 4 M guanidine HCl buffer containing 2% Triton X-100 and the proteoglycans were purified by ion exchange chromatography after extensive delipidation. Specific incorporation of 3H into GPI-anchor was demonstrated by removing the label with a phosphatidylinositol-specific phospholipase C (PI-PLC). Incorporation of 3H activity into glycosaminoglycans and core glycoproteins was also demonstrated. However, the specific activity of 3H in these structures was approximately 2 orders of magnitude lower than that in the GPI-anchor, suggesting that 3H label was the result of the metabolic utilization of catabolic products of the 3H-labeled fatty acids. PI-PLC treatment of cell cultures metabolically labeled with [3H]inositol, [3H]ethanolamine, or [32P]phosphate specifically released radiolabeled cell surface-associated HS proteoglycans indicating the presence of GPI-anchor in these proteoglycans. GPI-anchored HS proteoglycans accounted for 20-30% of the total cell surface-associated HS proteoglycans and virtually all of them were removed by PI-PLC. These results further substantiate the presence of GPI-anchored heparan sulfate proteoglycan in ovarian granulosa cells and its cell surface localization.
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PMID:Metabolic labeling of glycosylphosphatidylinositol-anchor of heparan sulfate proteoglycans in rat ovarian granulosa cells. 153 35


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