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)

Two enzymes, alkaline phosphatase and acetylcholinesterase (AChE), have been shown previously to be components of the surface of the trematode parasite Schistosoma mansoni. In this study we report that both these enzymes and other serine hydrolases are susceptible to release from the S. mansoni tegumental membrane by a phosphatidylinositol-specific phospholipase C (PIPLC) of bacterial origin. These data suggest that AChE and alkaline phosphatase of S. mansoni, as in higher organisms, are anchored to the membrane via covalently attached phosphatidylinositol. The release of AChE from the vesicular fraction of the parasite with PIPLC occurs in a concentration-dependent manner. Sucrose gradient centrifugation of the PIPLC-released AChE showed a single 8.3 S molecular form, similar to that observed for AChE solubilized by Triton X-100. PIPLC removed large amounts of AChE from the surface of intact schistosomula in culture, with no impairment of the viability of the parasite. In this case, an increase in the overall levels of AChE in the intact parasite was observed after addition of PIPLC.
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PMID:Acetylcholinesterase in Schistosoma mansoni is anchored to the membrane via covalently attached phosphatidylinositol. 313 66

To study the subcellular events occurring after T cell activation we used cloned human CTL permeabilized with alpha-toxin of Staphylococcus aureus. This method of permeabilization leads to stable transmembrane channels that permit the introduction of small molecules into the cell but preserves the cellular structures and macromolecular contents of the CTL. We used the exocytosis of CTL-specific serine esterases as a marker of T cell activation. The TCR-activated exocytosis is functioning in such permeabilized CTL. Introduction of the membrane impermeable guanosine nucleotide-binding protein (G-protein) activating GTP-analog GTP gamma S into CTL triggers exocytosis if Ca2+ is present. For optimal exocytosis ATP is required. The G-protein inactivating GDP-analog GDP beta S inhibited exocytosis triggered via the TCR-CD3 complex but not that triggered by activating the protein kinase C. If the protein kinase C was depleted in CTL by overnight incubation with phorbolester, the response to GTP-gamma S was reduced by more than 50%. These experiments demonstrate the presence of a G-protein involved in TCR-mediated CTL triggering. In the sequence of signaling steps this G-protein is localized after TCR-triggering but before the formation of the protein kinase C-activating phosphoinositol breakdown product diacylglycerol in the sequence of signaling steps.
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PMID:A T cell receptor-associated GTP-binding protein triggers T cell receptor-mediated granule exocytosis in cytotoxic T lymphocytes. 314 5

Insertion of the erythromycin resistance transposon Tn551 into a single site of the Staphylococcus aureus chromosome resulted in decreased production of alpha-toxin, serine and metallo-proteinases and several other extracellular proteins and a simultaneous increase in the production of protein A. The site of insertion, designated exp, was separate from the structural gene for alpha-toxin and protein A. Hybridization analysis showed that the effect of the insertional mutation on the expression of the alpha-toxin and protein A was at the level of transcription. The chromosomal DNA flanking the transposon and the corresponding DNA of the wild-type strain was cloned in Escherichia coli. Northern blot hybridization experiments revealed that the exp locus codes for a major RNA of approximately 3.5 kb. This RNA was not found in the insertional mutant nor in a spontaneous exp mutant. A map of the exp locus constructed by Northern blot and restriction enzyme analysis showed that the insertional mutation was located in the middle of the coding sequence of the 3.5 kb RNA. The insertional mutant was reverted to wild type by inserting a recombinant plasmid containing most of the coding sequence of the 3.5 kb RNA.
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PMID:Cloning of a chromosomal locus (exp) which regulates the expression of several exoprotein genes in Staphylococcus aureus. 328 38

An enzyme hydrolyzing sphingomyelin was purified from extracts of solid cultures of Aspergillus saitoi 7041 by fractionation with isopropanol followed by successive column chromatographies on DEAE-Sepharose CL-6B, butyl-Toyopearl 650 M, and phenyl-Sepharose CL-4B. The preparation of purified enzyme was homogeneous and had an activity increased 81-fold over that of the isopropanol fraction. The yield was about 65%. The molecular weight was estimated to be 54,000 by sodium dodecyl sulfate-gel electrophoresis. The enzyme solution had a violet color and contained iron atoms. The enzyme catalyzed the hydrolysis of sphingomyelin to N-acylsphingosine and phosphorylcholine. The optimum pH for hydrolytic activity was around 3.5. The Km values for sphingomyelin and 2-hexadecanoylamino-4-nitrophenylphosphorylcholine were 0.11 and 0.33 mM, respectively. The enzyme also catalyzed the hydrolysis of other phospholipids; the order of its hydrolytic activity at a substrate concentration of 2.5 mM was phosphatidylcholine greater than or equal to sphingomyelin = phosphatidylethanolamine = lysophosphatidylethanolamine greater than phosphatidyl DL-glycerol = phosphatidyl L-serine greater than phosphatidylinositol. From these results, this enzyme appears to be a new type of phospholipase C(phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3).
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PMID:Purification and properties of a phospholipase C that has high activity toward sphingomyelin from Aspergillus saitoi. 367 75

Primary cultures of mouse embryo palate mesenchyme cells were incubated with [3H]arachidonic acid and [14C]stearic acid in order to radiolabel their lipids. The cells were then washed, collected by centrifugation, and homogenized. Incubation of the homogenates under various conditions revealed that deoxycholate inhibited phospholipase A activity and stimulated a phospholipase C activity in these cells which preferentially degraded phosphatidylinositol (PI) compared to phosphatidylcholine (PC), -ethanolamine (PE), and -serine (PS). Expression of this phospholipase C (E.C. 3.1.4.10) activity was dependent on Ca2+ and had a pH optimum of no more than 7.0-7.5. Centrifugation of the homogenates at 105,000g for 30 min produced a membranous fraction that contained phospholipase C activity with characteristics similar to those of the enzyme found in the supernatant. Such a dual distribution of this enzyme may reflect that mouse embryo palate mesenchyme cells are neural crest in origin.
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PMID:Phospholipase C activity in palate mesenchyme cells: calcium and pH requirements, substrate specificity, and subcellular localization. 379 62

The phospholipid composition and the phospholipase C activity of envelope fractions of Escherichia coli B were determined with special consideration of fractions containing sites at which an attachment of inner and outer membranes had been observed in the electron microscope (Int.M). Phosphoglycerides labeled with [14C]palmitic acid and [3H]serine were extracted from membrane fractions and identified by two-dimensional thin-layer chromatography. The amount of phosphatidylethanolamine was highest in the outer membrane, whereas the amounts of phosphatidylglycerol and cardiolipin were highest in the inner membrane. The Int.M fractions were observed to have concentrations of phospholipids intermediate to those of the inner and outer membranes. This result supports the assumption that a concentration gradient of inner membrane-outer membrane lipids might exist at the membrane contact sites. The highest phospholipase C activity was detected in the inner membrane and Int.M fractions. The presence of phospholipase C and other lipolytic enzymes in the Int.M fractions suggests a possible involvement of adhesion sites in lipid metabolism, adding a further set of activities to the function of these domains.
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PMID:Phosphoglycerides and phospholipase C in membrane fractions of Escherichia coli B. 392 Feb 8

The domains of the acetylcholine receptor subunits that contact the lipid phase were investigated by hydrophobic photolabeling of receptor-rich membrane fragments prepared from Torpedo marmorata and Torpedo californica electric organs. The radioactive arylazido phospholipids used carry a photoreactive group, either at the level of the lipid polar head group (PCI) or at the tip of the aliphatic chain (PCII), and thus probe respectively the "superficial" and "deep" regions of the lipid bilayer. The four subunits of T. marmorata and T. californica acetylcholine receptor reacted with both the PCI and PCII probes and thus are all exposed to the lipid phase. Ligands known to stabilize different conformations of the acetylcholine receptor (nicotinic agonists, snake alpha-toxin, and noncompetitive blockers) did not cause any significant change in the labeling pattern. The acetylcholine receptor associated 43 000-dalton v1 protein did not react with any of the probes. A striking difference in labeling between T. marmorata and T. californica acetylcholine receptors occurred at the level of the alpha-subunit when the superficial PCI probe was used. An approximately 5-fold higher labeling of the alpha-subunit as compared to the beta-, gamma-, and delta-subunits was observed by using receptor-rich membranes from T. marmorata but not from T. californica. The same difference persisted after purification of the labeled receptors from the two species and was restricted to an 8000-dalton C-terminal tryptic peptide. The only mutation observed in this region of the complete alpha-subunit sequence of the two species is the substitution of cysteine-424 in T. marmorata by serine-424 in T. californica.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transmembrane topology of acetylcholine receptor subunits probed with photoreactive phospholipids. 402 35

Thrombin and trypsin induce serotonin release and aggregation in human platelets. Both proteases induce activation of phospholipase C as reflected by formation of inositol phosphates and phosphorylation of the resultant 1,2-diacylglycerol to phosphatidic acid. Also, thrombin and trypsin activate protein kinase C and myosin light chain kinase as indicated, respectively, by phosphorylation of the 40,000 and 20,000 dalton proteins. Leupeptin, a known inhibitor of serine proteases, blocks all the observed responses of human platelets to trypsin and thrombin. Leupeptin does not inhibit serotonin release and aggregation induced by other platelet stimuli such as collagen, platelet-activating factor, ionophore A23187, and arachidonic acid. The implication of a proteolytic-mediated pathway in the transmembrane signalling involved in platelet activation is discussed.
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PMID:Leupeptin selectively inhibits human platelet responses induced by thrombin and trypsin; a role for proteolytic activation of phospholipase C. 405 85

Human OC43 and bovine neonatal calf diarrhoea coronavirus (NCDCV) are known to be inhibited by non-antibody factors present in sera of different mammalian species, including man and cattle. Such an inhibitor is also present in fetal calf serum generally used for growing and maintaining cell cultures, thus influencing the viral infectivity titer. Previous reports refer to the effectiveness of phospholipase C treatment in eliminating the inhibiting activity. In order to detect the compound possibly involved in coronavirus growth inhibition (among the phospholipids naturally present in mammalian sera), we tested several phospholipids with hemagglutino-inhibition test and plaque reduction assay. Only phosphatidyl-serine seemed to be effective on Coronavirus OC43 and NCDCV, as detected by plaque-reduction assay, but not by hemagglutino-inhibition test.
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PMID:Phosphatidyl-serine inhibition of OC43 and NCDCV coronavirus infectivity. 406 11

The fatty acid selectivity of cytosolic phospholipase C (phosphatidylinositol phosphodiesterase) from pig and human platelets towards phosphatidylinositol was evaluated. For this purpose, the relative conversion of rat liver phosphatidylinositol (enriched in stearate and arachidonate) and sheep liver phosphatidylinositol (enriched in stearate plus oleate and containing linoleate and arachidonate) was compared and, in addition, the fatty acid compositions of the diacylglycerol products were determined by gas-liquid chromatography. The cytosolic enzyme exhibited essentially complete specificity for phosphatidylinositol when choline-, ethanolamine-, serine-, or inositol-containing phospholipids labelled with [14C]stearate were tested as substrates. Similar percentage conversions of rat and sheep liver phosphatidylinositols to 1,2-diacylglycerol were found with phospholipase C from either pig or human platelets. Furthermore, the newly formed diacylglycerols and the unreacted phospholipid had fatty acid compositions which were very similar to the corresponding substrates. These results suggest that the phospholipase C from isolated platelet cytosol is highly selective towards phosphatidylinositol, but not with respect to the fatty acid composition of naturally occurring phosphatidylinositol. They also suggest that any preferential release of arachidonoyl diacylglycerol in stimulated human platelets is more likely controlled by compartmentation of the corresponding phosphatidylinositol precursor within platelet membranes and its availability, rather than directly by a marked enzyme preference for arachidonate-containing species.
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PMID:Evaluation of the fatty acid selectivity of a phosphatidylinositol-specific cytosolic phospholipase C from pig and human platelets. 651 12


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