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)

Phospholipase A has been solubilized from the sarcoplasmic reticulum of rat heart by treatment with Tris buffer, potassium chloride, taurodeoxycholate or octyl glucoside. On HPLC gel permeation, two phospholipases were identified at the void volume of a TSK 3000 column and at an apparent molecular mass of 60 kDa. The two activity peaks exhibited a predominance of phospholipase A1 activity (83-91%) and a lesser phospholipase C activity (4-9%) using sonicated 1-palmitoyl-2[1-14C]oleoylphosphatidylcholine liposomes as substrate. The voiding phospholipase A peak, which represented the bulk of the recovered activity, exhibited a requirement for calcium ions in the 0.3-3 microM range. The heat stability and response to mercuric ions was studied and some similarities were noted between the solubilized sarcoplasmic reticulum phospholipases A and the cytosolic phospholipases A of rat heart. It is speculated that the cytosolic phospholipase A which we reported earlier may represent in part phospholipase A released from sarcoplasmic reticulum during isolation of the subcellular membrane fractions.
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PMID:Solubilization and partial characterization of phospholipase A from rat heart sarcoplasmic reticulum. 316 81

Amiodarone is used extensively for the chronic treatment of life-threatening arrhythmias caused by ischemic heart disease. However, chronic therapy with this agent results in phospholipidosis in various tissues and it has been suggested that the inhibition of lysosomal phospholipase A by this drug contributes to this abnormality. Exogenous amiodarone has been shown to inhibit purified rat liver lysosomal phospholipase A1, as well as acid phospholipase activities of alveolar macrophage homogenates and those of snake venom phospholipase A2 and bacterial phospholipase C. The effects of drug treatment on heart have not been explored. The results described here demonstrate that amiodarone also significantly increases (37%, p less than 0.001) phospholipid content in cat hearts. This increase is proportionately distributed to all major phospholipid classes, with the exception of sphingomyelin which appears to increase more than the others. In addition, the data also show that following amiodarone treatment, the endogenous drug levels in the heart were sufficient to reduce in vitro losses of membrane phospholipid at 37 degrees C by inhibiting a variety of endogenous phospholipases at physiological (7.4), ischemic (6.2) and acidic (5.0) pH values. This protection is more pronounced at acidic pH values than at physiological pH. Endogenous amiodarone also affects myocardial phospholipase activities towards exogenous phosphatidylcholine and again the extent of inhibition is more at acidic pH. These results suggest that amiodarone induces phospholipidosis in the heart by inhibiting phospholipid catabolism and that its antiarrhythmic properties may reside in its ability to modulate alkaline, neutral and acid phospholipase activities in ischemia. To what extent amiodarone metabolites (desethylamiodarone and bis-desethylamiodarone) are involved in these actions remains to be determined.
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PMID:Effects of chronic amiodarone treatment on cat myocardial phospholipid content and on in vitro phospholipid catabolism. 345 65

The enzyme GDPFuc:GM1 alpha 1----2 fucosyltransferase, induced by chemical carcinogens in precancerous rat liver as well as rat hepatoma cells, was found previously to be membrane bound, and was inactivated by various detergents, while the activities of many other transferases are generally enhanced by detergents (Holmes, E.H. & Hakomori, S. (1983) J. Biol. Chem. 258, 3706-3717). The effects of phospholipids and detergents on rat hepatoma H35 cells, the conditions of solubilization and subsequent affinity chromatography of the enzyme, and a possible association of phospholipids with the enzyme have been studied with the following major results: The alpha 1----2 fucosyltransferase activity in Golgi membrane was diminished on treatment of membranes with phospholipase A1 or phospholipase C. The enzyme activity was stimulated 7-fold in the presence of cardiolipin or phosphatidylglycerol (and 3-fold by phosphatidylethanolamine) but not other phospholipids. The stimulatory effect of phosphatidylglycerol was eliminated when a variety of ionic or non-ionic detergents were added to the reaction mixture, with the exception of the cationic detergent G-3634-A, which provided a 10-fold total stimulation in the presence of phosphatidylglycerol. The kinetic analysis indicated that addition of phosphatidylglycerol has a negligible effect on apparent Km values but increases the Vmax of the enzyme 5- to 6-fold. The enzyme activity was solubilized by the dialyzable detergent CHAPSO without inhibition of the enzyme activity, and the solubilized enzyme in the presence of 0.4% CHAPSO is partially purified by chromatography on GDP-hexanolamine-Sepharose. Removal of CHAPSO from the affinity purified enzyme by dialysis resulted in a 66% loss of the original activity, which was restored by addition of phosphatidylglycerol. Chromatography of the affinity-purified enzyme with 3H-labeled phosphatidylglycerol on a Biogel A0.5 column indicated an association of the enzyme with the phospholipid that occurred only in the absence of detergent. These results suggest that phospholipid has a direct effect on the enzyme and that the inhibitory effect of detergents can be ascribable to disturbing interaction between phospholipids and the enzyme. A possible role of specific phospholipids on in vivo transferase activity for glycolipids is discussed.
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PMID:The chemical carcinogen-induced enzyme, GDP-fucose: GM1 alpha 1----2 fucosyltransferase in rat liver and hepatoma: modulation by and association with phospholipids. 365 87

The results of recent studies support the concept that Ureaplasma urealyticum may be a major cause of perinatal infection in both term and preterm infants. It has been postulated that phospholipase degradation of placental phospholipids by microorganisms triggers the onset of premature labor. Since the presence of ureaplasmas in placentas is associated with pregnancy loss, prematurity, and neonatal morbidity, we assayed U. urealyticum for the presence of phospholipase A1, A2, and C activities. Phospholipase A1 activity was low in lysates of exponential-phase cells of U. urealyticum. Phospholipase A2 activity was present and was 100-fold higher than the activity of phospholipase A1 in serotypes 3,4, and 8. The total activity and specific activity of phospholipase A2 in serotype 8 were nearly threefold higher than the activities in serotypes 3 and 4. Cell lysates of all three serotypes showed the presence of phospholipase C activity during the exponential phase of growth, and no significant difference in activity was observed among the three serotypes. In stationary-phase cells the phospholipase C activity was 10-fold lower than the activity in exponential-phase cells. Our results demonstrate that phospholipase activities are present in U. urealyticum cells and that the specific activities of phospholipase A2 differed among the three serotypes tested, while the activities of phospholipases A1 and C were similar.
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PMID:Endogenous activity of phospholipases A and C in Ureaplasma urealyticum. 370 Jun 18

The murine macrophage (M phi) cell line, P388D1, was employed as a source of M phi phospholipases in order to characterize the enzymatic properties and subcellular localization of these enzymes because of their importance for prostaglandin biosynthesis. Phospholipase activity was assessed with dipalmitoylphosphatidylcholine (DPPC) as substrate. Phospholipases were characterized with respect to divalent cation dependence, pH optima, and localization in subcellular compartments using linear sucrose gradients. By these criteria a number of different phospholipases were identified. Most importantly, a single Ca2+-dependent activity with a pH optimum of 8.8 was identified in membrane-rich fractions (plasma membrane, mitochondria, and endoplasmic reticulum) and could be clearly separated from the remaining activities, which are Ca2+ independent and exhibit pH optima of 7.5, 5.1, and 4.2. The phospholipases with acidic pH optima may be associated with subcellular components containing lysosomal enzymes and both phospholipase A1 and phospholipase A2 activities are observed. In contrast, the phospholipase activity with a pH optimum of 7.5 sediments with the cytosolic proteins and is inhibited by 5 mM Ca2+. No significant phospholipase C activity was detected in assays performed with or without added Ca2+ at pH's 4.2, 5.1, 7.5, or 8.8 using DPPC as substrate. However, the P388D1 cells do contain a lysophospholipase that is at least 20 times more active than the phospholipase A activities identified. Its presence must be taken into account in evaluating the positional specificities and properties of the macrophage phospholipases.
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PMID:Phospholipase activities of the P388D1 macrophage-like cell line. 398 20

Non-competitive inhibition of snake venom phospholipase A2 which has been exhibited by bovine plasma phospholipase A inhibitor, a kind of lipoprotein, was not observed unless the inhibitor was preincubated with the enzyme. The inhibition seemed to be due to the formation of the enzyme-inhibitor complex, which was identified by immunoelectrophoresis. The enzyme-inhibitor interaction was observed maximally on incubation at physiological pH, but not below pH 5. The inhibitor was inactivated by trypsin digestion and heat treatment. It suppressed the phospholipase A2 activities of rat blood plasma as well as of the snake venom and porcine pancreas, but not the enzyme activities such as those of phospholipase C of Bacillus cereus, lipase of porcine pancreas, trypsin, and papain. The inhibitor also showed the ability to decrease membrane-bound phospholipase A1 and A2 activities in intracellular organelles such as plasma membranes, mitochondria, lysosomes, and microsomes. In view of these facts, it was concluded that the plasma inhibitor is specific for phospholipase A.
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PMID:Studies on phospholipase A inhibitor in blood plasma. II. Interaction of phospholipase A inhibitor with phospholipase A and its specificity. 404 47

Previous studies have reported an increased turnover of phospholipid in isolated islets of Langerhans in response to raised glucose concentrations. The present investigation was thus undertaken to determine the nature of any phospholipases that may be implicated in this phenomenon by employing various radiolabelled exogenous phospholipids. Hydrolysis of 1-acyl-2-[14C]arachidonoylglycerophosphoinositol by a sonicated preparation of islets optimally released radiolabelled lysophosphatidylinositol, arachidonic acid and 1,2-diacylglycerol at pH 5,7 and 9 respectively. This indicates the presence of a phospholipase A1 and a phospholipase C. However, the lack of any labelled lysophosphatidylinositol production when 2-acyl-1-[14C]stearoylglycerophosphoinositol was hydrolysed argues against a role for phospholipase A2 in the release of arachidonic acid. Phospholipase C activity as measured by phosphatidyl-myo-[3H]inositol hydrolysis was optimal around pH8, required Ca2+ for activity and was predominantly cytosolic in origin. The time course of phosphatidylinositol hydrolysis at pH 6 indicated a precursor-product relationship for 1,2-diacylglycerol and arachidonic acid respectively. The release of these two products when phosphatidylinositol was hydrolysed by either islet or acinar tissue was similar. However, phospholipase A1 activity was 20-fold higher in acinar tissue. Substrate specificity studies with islet tissue revealed that arachidonic acid release from phosphatidylethanolamine and phosphatidylcholine was only 8% and 2.5% respectively of that from phosphatidylinositol. Diacylglycerol lipase was also demonstrated in islet tissue being predominantly membrane bound and stimulated by Ca2+. The availability of non-esterified arachidonic acid in islet cells could be regulated by changes in the activity of a phosphatidylinositol-specific phospholipase C acting in concert with a diacylglycerol lipase.
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PMID:Phosphatidylinositol hydrolysis in isolated guinea-pig islets of Langerhans. 636 63

Hydrolysis of 2-[1-14C]oleoyl phosphatidylcholine and of 1-[1-14C]oleoyl lysophosphatidylcholine by lysosomes prepared from rat liver using Triton WR-1339 has been studied. At pH 5.0 sodium taurocholate stimulated the release by the soluble lysosomal fraction of labelled lysophosphatidylcholine, diacyl- and monoacylglycerol and fatty acids from [14C]phosphatidylcholine. The time course of appearance of labelled products suggested that monoacylglycerol could be released as a result of the action of phospholipase A1 followed by lysophospholipase C or by the initial action of phospholipase C followed by monoacylglycerol lipase. The hydrolysis of 1-[14C]acyl lysophosphatidylcholine was also stimulated by sodium taurocholate under similar conditions; however, only release of monoacylglycerol was increased, whereas release of fatty acid was inhibited. Mg2+ inhibited the release of labelled monoacylglycerol and of fatty acid from lysophosphatidylcholine. The detergents deoxycholate and Triton X-100 and phospholipids were strongly inhibitory. 5'-AMP almost completely suppressed release of monoacylglycerol but increased release of fatty acid. Chloroquine strongly suppressed release of monoacylglycerol and only at high concentration (1.25 mM) diminished fatty acid release. In the presence of sodium taurocholate the predominant mechanism for degradation of phosphatidylcholine by the soluble fraction of lysosomes involves phospholipase A followed by phospholipase C. Assay of release of monoacylglycerol from [14C]lysophosphatidylcholine catalyzed by extracts of fibroblasts from patients with Niemann-Pick disease and controls in the presence of taurocholate revealed that lysophospholipase C activity was lacking in those cell lines that were deficient in sphingomyelinase. This suggests that lysophospholipase C and sphingomyelinase activities may be catalyzed by one enzyme.
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PMID:Degradation of lysophosphatidylcholine by lysosomes. Stimulation of lysophospholipase C by taurocholate and deficiency in Niemann-Pick fibroblasts. 673 21

Radioactive phosphatidyl choline substrates specifically labeled in the one position or two position fatty acid were used to establish conditions for the detection of acidic phospholipase A1, A2 and C activities in extracts of cultured human fibroblasts. Maximal activity was detected at a pH of 3.0, 4.0 and 5.0 respectively, suggesting that the enzymes are of lysosomal origin. None of the activities were stimulated or inhibited markedly by Ca2+ or EDTA. The A1 and A2 activities, but not the C activity, were inactivated by the sulfhydryl reactive Ellman reagent. All three enzyme activities were in the normal range for cultured fibroblasts which were deficient in acid lipase, indicating that these activities are not attributable to the acid lipase gene product. Phospholipase A activity was deficient in fibroblast extracts from patients with Niemann-Pick disease, types A, B and C. These data suggest either identity or a genetic relationship between sphingomyelinase and phospholipase C. The activities examined were within the normal range in fibroblasts from patients with neuronal ceroid lipofuscinosis, sea blue histiocyte disease and selected uncharacterized degenerative diseases.
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PMID:Acidic phospholipases in cultured human fibroblasts: deficiency of phospholipase C in Niemann-Pick disease. 678 96

To investigate the type of phospholipase activated by agents that stimulate prostaglandin synthesis, we used transformed mouse cells whose phospholipids were doubly labeled with [14C]inositol and [3H]arachidonic acid. [14C]Inositol was incorporated mostly into the phosphatidylinositol and [3H]arachidonic acid was distributed into the various phospholipids. When these cells were incubated with bradykinin, a stimulator of prostaglandin synthesis, the release of 3H radioactivity from cellular phospholipids and the synthesis of prostaglandin were initiated within seconds and reached a maximum in 40 to 70 s. Analysis of the intracellular lipids revealed a concomitant increase of radioactivity associated with lysophosphatidylinositol, which was detectable within 5 s of incubation with bradykinin and reached a maximum between 40 and 70 s. Lysophosphatidylinositol which could be formed either from a phospholipase A1 or phospholipase A2 reaction, was identified by its chromatographic properties and conversion to glycerophosphorylinositol. We found that the 3H/14C ratio of purified lysophosphatidylinositol was 1/11 of that of phosphatidylinositol, which indicated that lysophosphatidylinositol formed in response to bradykinin is 1-acyl-sn-glycero-3-phosphorylinositol and most probably is formed from a phospholipase A2 deacylation of phosphatidylinositol (a phospholipase A1 deacylation would result in the formation of lysophosphatidylinositol of a 3H/14C ratio similar to phosphatidylinositol). Furthermore, we did not detect between control and stimulated cells any significant difference in the level of several phospholipase C metabolites including inositol phosphate, diglyceride, and phosphatidic acid. These results suggest that phospholipase C is probably not activated. The formation of lysophosphatidylinositol was also stimulated by thrombin and ionophore A23187, both activators of prostaglandin synthesis. Dexamethasone, a lipase inhibitor, inhibited the appearance of lysophosphatidylinositol, whereas aspirin and low concentrations of indomethacin, the cyclooxygenase inhibitor, did not inhibit. The results presented in ths paper provide evidence that a phospholipase A2-hydrolyzing phosphatidylinositol is activated when intact cells are stimulated for prostaglandin synthesis.
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PMID:The activation of phosphatidylinositol-hydrolyzing phospholipase A2 during prostaglandin synthesis in transformed mouse BALB/3T3 cells. 678 79


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