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)

A novel membrane-bound glycan-phosphatidylinositol-specific phospholipase C, which catalyzes the conversion of membrane form variant surface glycoproteins to soluble variant surface glycoproteins, with the release of sn-1,2-dimyristylglycerol, has been isolated from Trypanosoma brucei. The activity was solubilized from trypanosome membrane fractions in non-ionic detergent and purified by anion exchange chromatography on DEAE-cellulose followed by chromatography on phosphatidylinositol-Sepharose. The enzyme constitutes about 0.1% of the total cellular protein and has an apparent molecular weight of 39,800. The enzyme shows a head group specificity for molecules containing carbohydrate covalently linked to glycan-phosphatidylinositol, but can also act on the monoacyl derivative of membrane form variant surface glycoprotein. It shows no specific ion requirements but is stimulated by thiol-reducing agents and inhibited by ions that thiols chelate.
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PMID:Purification and characterization of a novel glycan-phosphatidylinositol-specific phospholipase C from Trypanosoma brucei. 378 89

Three different phospholipases C--the so-called phospholipase C which hydrolyses phosphatidylcholine (Pch-PLC), sphingomyelinase (SM-PLC) and phosphatidylinositol hydrolysing phospholipase C (PI-PLC)--were separated from the culture filtrate of Bacillus cereus using column chromatography on DEAE-sephadex A-50. The pI values were estimated to be 5.0 +/- 0.3 for PI-PLC and 5.3 +/- 0.2 for SM-PLC. The effect of some bivalent cations was studied. Metal ions had no effect on the activity of PI-PLC, whereas Mg2+ and Co2+ in concentrations from 1 to 5 mM highly activated SM-PLC. Mg2+ failed to activate PCh-PLC, and Co2+ even inhibited it. EDTA of o-phenantroline had a rather inhibitory effect on Pch-PLC, but they almost did not affect SM-PLC.
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PMID:[Properties of the phospholipases C from Bacillus cereus]. 392 53

Two novel phospholipase activities have been identified in the cytosolic fraction of canine myocardium. Neutral active phospholipase C activity was partially purified by anion exchange, hydroxylapatite, chromatofocusing, and gel filtration chromatographies. The partially purified enzyme had similar maximum velocities (237 versus 241 nmol/mg X h) and apparent Michaelis constants (20 versus 14 microM) utilizing either plasmenylcholine or phosphatidylcholine as substrate. Myocardial phospholipase C had a pH optimum between 7 and 8, required divalent cations for maximal activity, and did not hydrolyze phosphatidylinositol or sphingomyelin. Myocardial cytosol contained a potent inhibitor of phospholipase C which masked enzymic activity until it was removed during the purification procedure. A plasmalogen selective phospholipase A2 activity was also identified in the cytosolic fraction of canine myocardium. The protein catalyzing this activity was partially purified by DEAE-Sephacel-hydroxylapatite tandem chromatography and exhibited a maximum velocity of 5 nmol/mg X h for plasmenylcholine but only 1 nmol/mg X h for phosphatidylcholine, had a pH optimum between 6 and 7 for both substrates, and did not require calcium ion for activity. These results constitute the first demonstration of a neutral active phospholipase C specific for choline and ethanolamine glycerophospholipids and a plasmalogen selective phospholipase A2 in mammalian tissue.
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PMID:Identification of neutral active phospholipase C which hydrolyzes choline glycerophospholipids and plasmalogen selective phospholipase A2 in canine myocardium. 399 69

The effect of mepacrine (DL-quinacrine-HCI), a specific inhibitor of phospholipase C, on cyclic-GMP levels in human platelets was investigated. The concentrations of mepacrine producing 50% inhibition of human platelet aggregation induced by 5 microM ADP and 3 micrograms/ml of collagen were 50 +/- 8 and 70 +/- 15 microM, respectively. Addition of mepacrine to human platelet suspension resulted in increases in cyclic GMP. In contrast to cyclic-GMP levels, cyclic-AMP content was not affected by mepacrine. Mepacrine did not stimulate guanylate cyclase, but did specifically inhibit human platelet cyclic-GMP phosphodiesterase, separated from cyclic-AMP phosphodiesterase or other forms of phosphodiesterase on DEAE-cellulose columns. Stimulation by cyclic GMP of human platelet cyclic-GMP-stimulated cyclic-AMP phosphodiesterase activity was not inhibited by mepacrine. The IC50 value of the drug for cyclic-GMP phosphodiesterase was 40 microM, and IC50 for cyclic-AMP phosphodiesterase was 1.2 mM. Mepacrine was 30-times more potent as an inhibitor of human platelet cyclic GMP than of cyclic-AMP phosphodiesterase. Mepacrine blocks arachidonate release from human platelets by inhibiting phosphatidylinositol-specific phospholipase C. The increase in cyclic-GMP levels produced by addition of mepacrine will explain part of the pharmacological action of this drug.
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PMID:Mepacrine-induced inhibition of human platelet cyclic-GMP phosphodiesterase. 614 62

Incubation of human platelets with C. perfringens phospholipase C caused an increase in soluble protein kinase activity assayed in the presence of EGTA, and a decrease in Ca2+/phospholipid-dependent protein kinase activity. Fractionation of extracts on DEAE-cellulose columns showed that phospholipase C treatment resulted in a new peak of protein kinase active in the presence of EGTA. On Sephadex G-100 chromatography this enzyme eluted as a single peak of protein kinase activity of MW about 50,000. An extract from untreated platelets eluted as a single peak of Ca2+/phospholipid-dependent protein kinase of MW about 77,000. It was concluded that phospholipase C treatment resulted in the proteolysis of this latter enzyme to the lower MW form.
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PMID:Platelet Ca2+-activated, phospholipid-dependent protein kinase: evidence for proteolytic activation of the enzyme in cells treated with phospholipase C1. 623 Oct 25

A specific binding site for somatotropin was solubilized by 1% (v/v) Triton X-100 from a crude particulate membrane fraction of pregnant rabbit liver, partially purified and characterized. The solubilized binding site retained many of the characteristics observed in the original particulate fraction, indicating that extraction of the binding site with Triton X-100 does not cause any major changes in its properties. The binding of human 125I-labelled-somatotropin to the solubilized binding site is a saturable and reversible process, depending on temperature, incubation time, pH and ionic environment. Analysis of the kinetic data revealed a finite number of binding sites with an affinity constant of 0.32 x 10(10)M-1. The binding activity for human 125I-labelled-somatotropin was adsorbed to a concanavalin-A-Sepharose column and was dissociated from the column with alpha-methyl-D-glucoside, suggesting that the binding protein may be a glycoprotein. Using affinity chromatography on concanavalin-A-Sepharose, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sepharose 6B, the binding protein was purified 1000-4000-fold from the original liver homogenate. When the partially purified preparation was chromatographed on Sepharose 6B, the binding protein eluted as a molecule with an apparent molecular weight of 200000, with a Stokes' radius of 4.9 nm. Sucrose-density-gradient centrifugation of the preparation showed that the sedimentation coefficient of the binding protein was 7.2S. Isoelectric focusing experiments revealed that a major part of the protein has an acidic pI (4.2-4.5). Exposure of the protein to trypsin decreased the binding activity for human 125I-labelled-somatotropin or bovine 125I-labelled-somatotropin, whereas ribonuclease, deoxyribonuclease, phospholipase C or neuraminidase had little or no effect.
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PMID:Characteristics of solubilized human-somatotropin-binding protein from the liver of pregnant rabbits. 624 70

A procedure has been developed for the separation of intrinsic proteins of plasma membranes from the electric organ of Torpedo marmorata. (Na+ + K+)-ATPase, nicotinic acetylcholine receptor and acetylcholinesterase remained active after solubilization with the nonionic detergent dodecyl octaethylene glycol monoether (C12E8). These components could be separated by ion exchange chromatography on DEAE-Sephadex A-25. Fractions enriched in ouabain-sensitive K+-phosphatase or (Na+ + K+)-ATPase activity showed two bands in sodium dodecyl sulphate polyacrylamide gel electrophoresis corresponding to the alpha- and beta-subunits. The (Na+ + K+)-ATPase was shown to have immunological determinants in common with a 93 kDa polypeptide which copurified with the nicotinic acetylcholine receptor, also after solubilization in Triton X-100 and chromatography on Naja naja siamensis alpha-toxin-Sepharose columns. The data suggest that the alpha-subunit of (Na+ + K+)-ATPase associates with the acetylcholine receptor in the membranes of the electric organ.
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PMID:Fractionation of protein components of plasma membranes from the electric organ of Torpedo marmorata. 629 54

Stimulated human platelets are known to undergo marked and rapid changes in phosphoinositide metabolism consistent with the activation of phospholipase C. Such changes may promote a Ca2+ flux after platelets are exposed to agonists. I have examined this enzymatic activity by using disrupted platelets. When human platelets are sonicated and then incubated with phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2) or phosphatidylinositol 4-monophosphate (PtdIns4P) in the presence of Ca2+ and deoxycholate, marked hydrolysis of these substrates occurs. Characterization of the hydrolysis products by anion exchange and thin-layer chromatography indicates that the bulk of this activity is enzymatic and attributable to phospholipase C. In the absence of Ca2+ or deoxycholate, only phosphomonoesterase activity is observed. I partially purified the soluble phospholipase C on DEAE-cellulose in order to minimize phosphomonoesterase activity. Fractions eluting at low salt concentrations contain the highest phospholipase C activity with respect to PtdIns4,5P2 and PtdIns4P and the lowest phosphomonoesterase activity. The enzyme(s) in these fractions is (are) maximally active in the presence of 0.1 mM Ca2+ and deoxycholate (1 mg/ml) and display(s) substrate affinities in the order PtdIns greater than PtdIns4P greater than PtdIns4,5P2 and maximum rates in the order PtdIns4P greater than PtdIns4,5P2 greater than PtdIns. This order of substrate preference appears to differ from that observed for physiologically stimulated cells. Possible reasons for such a discrepancy are discussed.
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PMID:Human platelets contain phospholipase C that hydrolyzes polyphosphoinositides. 631 May 76

Sheep brain membrane opiate receptors were solubilized using two different approaches: (A) Chaps was used to solubilize [3H]buprenorphine labeled membranes. Macromolecular labeled material had a stokes radius of approximately 90 A. Treatment with phospholipase A2, but not phospholipase C, decreased the stokes radius to 50 A indicating the presence and eventual structural role of phospholipids in the solubilized opiate receptor complex. (B) Digitonin-NaCl was used for solubilization of receptors which were then labeled with [3H]diprenorphine. This complex could be chromatographed on hydroxylapatite, DEAE-sepharose and phenylboronate gels successively permitting an approximately 100-fold purification over the solubilized starting material.
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PMID:Chromatography and partial purification of solubilized opiate receptors. 631 61

The mode of acetylcholinesterase release from mammalian erythrocyte membranes by the action of phosphatidylinositol(PI)-specific phospholipase C of Bacillus thuringiensis was studied. As regards intact erythrocytes, a larger amount of acetylcholinesterase was released from sheep or bovine erythrocytes than from horse erythrocytes. From horse erythrocyte ghosts, acetylcholinesterase was more easily released than from intact cells. Bovine erythrocyte acetylcholinesterase released by PI-specific phospholipase C was purified by column chromatography on DEAE-cellulose, affinity gel and Sepharose 6B, to a homogeneous state, as indicated by polyacrylamide gel electrophoresis, with a recovery of 39%. Also, bovine erythrocyte acetylcholinesterase was solubilized by Triton X-100 and partially purified. The properties of these acetylcholinesterase preparations obtained by the action of PI-specific phospholipase C and/or Triton X-100 were studied in detail. On elution from the Sepharose 6B column, Triton X-100-solubilized acetylcholinesterase was eluted at the void volume while the enzyme obtained by further treatment with PI-specific phospholipase C was eluted in the region corresponding to M.W. 250,000. Furthermore, the heat stability of acetylcholinesterase purified after solubilization with PI-specific phospholipase C was higher than that of the Triton X-100-solubilized acetylcholinesterase. The close association and direct interaction of PI with acetylcholinesterase in the erythrocyte membrane was suggested by the above results.
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PMID:Acetylcholinesterase release from mammalian erythrocytes by phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis and characterization of the released enzyme. 650 Dec 51


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