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)

We have investigated the mechanism by which estrogen stimulates phosphatidylcholine synthesis in fetal rabbit lung. The hormone increased the activity of cholinephosphate cytidylyltransferase in the 105 000 X g supernatant fraction but had no effect on the activities of this enzyme in the homogenate or other subcellular fractions. Although microsomal cytidylyltransferase has been reported to regulate phosphatidylcholine synthesis in other systems, and translocation of the enzyme from cytosol to microsomes has been reported in association with increased phosphatidylcholine synthesis, we found no evidence of this in the case of estrogen-stimulated phosphatidylcholine synthesis in the fetal lung. Cytosolic cytidylyltransferase activity was dependent on phospholipids. Extraction with acetone/butanol drastically reduced its activity as well as the stimulatory effect of estrogen. The activity and the effect of estrogen were restored on re-addition of lipids extracted with chloroform/methanol from additional supernatants. Fractionation of the total lipids revealed that the stimulatory effect was entirely associated with the phospholipids; neutral lipids and glycolipids did not stimulate. Treatment of the phospholipid fraction with phospholipase C abolished the stimulatory effect. The stimulatory effect of estrogen, however, could not be attributed to any individual phospholipid species but appeared to require the entire phospholipid mixture. We conclude that estrogen stimulates fetal lung phosphatidylcholine synthesis by increasing the activity of cytosolic cytidylyltransferase and this activation in turn is mediated by cytosolic phospholipids.
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PMID:Stimulation of cholinephosphate cytidylyltransferase activity by estrogen in fetal rabbit lung is mediated by phospholipids. 298 5

We have employed a neutral-pH extraction technique to look for inositol 1,2-cyclic phosphate derivatives in [3H]inositol-labelled parotid gland slices stimulated with carbachol. The incubations were terminated by adding cold chloroform/methanol (1:2, v/v), the samples were dried under vacuum and inositol phosphates were extracted from the dried residues by phenol/chloroform/water partitioning. Water-soluble inositol metabolites were separated by h.p.l.c. at pH 3.7. 32P-labelled inositol phosphate standards (inositol 1-phosphate, inositol 1,2-cyclic phosphate, inositol 1,4,5-trisphosphate and inositol 1,2-cyclic 4,5-trisphosphate) were quantitively recovered through both extraction and chromatography steps. Treatment of inositol cyclic phosphate standards with 5% (w/v) HClO4 for 10 min prior to chromatography resulted in formation of the expected non-cyclic compounds. [3H]Inositol 1-phosphate and [3H]inositol 1,4,5-trisphosphate were both present in parotid gland slices and both increased during stimulation with 1 mM-carbachol. There was no evidence for significant quantities of [3H]inositol 1,2-cyclic phosphate or [3H]inositol 1,2-cyclic 4,5-trisphosphate in control or carbachol-stimulated glands. Parotid gland homogenates rapidly converted inositol 1,4,5-trisphosphate to inositol bisphosphate and inositol tetrakisphosphate, but metabolism of the inositol cyclic trisphosphate was much slower. The results suggest that inositol 1,4,5-trisphosphate, but not inositol 1,2-cyclic 4,5-trisphosphate, is the water-soluble product of muscarinic receptor-stimulated phospholipase C in rat parotid glands.
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PMID:Inositol 1,2-cyclic 4,5-trisphosphate is not a product of muscarinic receptor-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis in rat parotid glands. 303 79

Phospholipase C and 1,2-diacylglycerol lipase activities were demonstrated in human endometrium using 1-stearoyl-2-[1-14C]arachidonyl phosphatidylinositol as substrate. Phosphatidylinositol is hydrolysed by phospholipase C to inositol phosphates and to 1,2-diacylglycerol which is then further metabolized by 1,2-diacylglycerol lipase to release free arachidonic acid. In the present study the radiolabelled products formed (1,2-diacylglycerol and arachidonic acid) were measured following chloroform/methanol extraction and thin-layer chromatography. Phospholipase C activity was calcium dependent and optimal at pH 5.0-5.5 and 7.5; 1,2-diacylglycerol lipase activity was also calcium dependent, with an optimum pH of 5.5. A significant increase in 1,2-diacylglycerol production was stimulated by steroid sulphates. Pregnenolone sulphate, oestrone sulphate, testosterone sulphate and dehydroepiandrosterone sulphate stimulated 4, 3.2-, 1.8- and 2.6-fold increases in release respectively. Oestradiol sulphate stimulated a 25% increase in diacylglycerol release which was not significantly different from the control value. Progesterone stimulated a fourfold increase but other free steroids had no effect. Arachidonic acid release was increased in the presence of oestradiol sulphate, oestrone and oestradiol but reduced by oestrone sulphate, dehydroepiandrosterone sulphate, progesterone, dehydroepiandrosterone and, to a lesser extent, by pregnenolone sulphate and testosterone sulphate. 5-Androstene-3 beta,17 beta-diol had no effect on the liberation of either product. This study demonstrates a potential route for the liberation of arachidonic acid from phosphatidylinositol in human endometrium. The opposing effects of steroids on phospholipase C and 1,2-diacylglycerol lipase activity could be important in regulating the release of arachidonic acid by this pathway.
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PMID:Hydrolysis of phosphatidylinositol by human endometrium: modulating effects of steroids on arachidonic acid and 1,2-diacylglycerol release. 337 59

In this paper we report the detection of phospholipase C activity in cultured human skin fibroblasts by a rapid, sensitive method. Sonicates of fibroblasts were incubated with L-3-phosphatidyl-[U-14C]-inositol and the incubation mixture extracted with chloroform/methanol. The solvent components were then separated into 2 phases by the addition of 2 M KCl. Phospholipase C activity, determined from the amount of [14C] in the aqueous phase, agreed well with the enzyme activity assessed by other methods. The optimum pH for the enzyme was 7.0 and the enzyme was found to be dependent on Ca2+ and deoxycholate for optimal activity. The demonstration of phospholipase C activity by this method in cultured skin fibroblasts provides a useful means with which to study, in human tissues, the physiological control of this enzyme and its derangements in disease states in a controlled fashion.
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PMID:Phospholipase C activity in cultured human skin fibroblasts. 360 41

Bacillus cereus phospholipase was characterized as a phospholipase C by the analysis of lecithin degradation products by thin-layer and paper chromatography. Methanol in the growth menstruum inhibited completely the synthesis of phospholipase C, whereas the synthesis of lethal toxin and hemolysin were only partially inhibited. Dialysis of preformed B. cereus products against ethyl alcohol and methanol did not inactivate hemolytic, phospholipase C, or lethal activity. The hemolytic and lethal activities of culture filtrates were completely abolished by trypsin, but phospholipase C activity was resistant to inactivation. Lethal and phospholipase C properties of culture filtrates were resistant to inactivation at 45 C, whereas the hemolytic activity was completely destroyed. Lethal, hemolytic, and phospholipase C activities appeared simultaneously in a complex growth menstruum, but the kinetics of synthesis were different in all cases. Resolution of B. cereus filtrates on columns of Sephadex showed that the phospholipase C, hemolysin, and lethal toxin are distinct proteins. Evidence is also presented which suggests a correlation between the synthesis of B. cereus toxin and the period of transition from vegetative growth to sporulation. The activity of each B. cereus product was cation-independent, as opposed to cation-dependency of the phospholipase C and lethal activities of Clostridium perfringens alpha-toxin. Immunological cross-reactivity between the B. cereus products and C. perfringens alpha-toxin was not apparent; indeed, they were shown to be antigenically distinct.
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PMID:Lethal toxin of Bacillus cereus. I. Relationships and nature of toxin, hemolysin, and phospholipase. 429 11

Platelets stimulate tissue factor, the initiator of the extrinsic coagulation pathway, and increase fibrinolytic inhibition in fibroblasts grown in vitro. Cellular tissue factor increases an average of 2.8-fold over the control levels after a 6-hr incubation with platelets, and no activity is present in the media. Fibrinolytic inhibition is stimulated in both the fibroblasts and their media in the presence of platelets and accumulates throughout a 24-hr incubation. Neither leukocytes nor erythrocytes stimulate these changes. Both tissue factor and fibrinolytic inhibition increases are dependent on platelet concentration and are blocked by inhibitors of RNA or protein synthesis. Control smooth muscle cells have higher tissue factor and fibrinolytic inhibition than fibroblasts, but their response to the presence of platelets is similar. Confluent monolayers of endothelial cells have very low levels of tissue factor that are not altered by the presence of platelets. However, the ability of endothelial cells to inhibit fibrinolysis is enhanced by the presence of platelets. The fraction that stimulates tissue factor and fibrinolytic inhibition is distinct from platelet-derived growth factor and from the fraction that enhances leukocyte tissue factor. It is associated with an insoluble, nonmitogenic fraction that is not inactivated by phospholipase C, or diisopropylfluorophosphate, nor is it chloroform:methanol extractable. Platelets are a physiologic modulator for both cellular tissue factor and the fibrinolytic system in vitro.
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PMID:Platelet effects on tissue factor and fibrinolytic inhibition of cultured human fibroblasts and vascular cells. 617 62

Recently we described a saturable, high-affinity binding site for vesicular stomatitis virus (VSV) on the surface of Vero cells that appears to mediate viral infectivity. To isolate this binding site, we have extracted Vero cells with the detergent, octyl-beta-D-glucopyranoside. The dialyzed detergent extract specifically inhibits the saturable, high-affinity binding of 35S-methionine-labeled VSV to Vero cells. The inhibitory activity is resistant to protease, neuraminidase and heating to 100 degrees C. It is soluble in chloroform-methanol and inactivated by phospholipase C, suggesting that it is a phospholipid. Of various purified lipids tested, only phosphatidylserine was capable of totally inhibiting the high-affinity binding of VSV. The half-maximal inhibitory concentration for phosphatidylserine was 1 microM. Phosphatidylserine also inhibited VSV plaque formation by 80%-90%; Herpes simplex virus plaque formation was unaffected. Centrifugation and electron microscopy studies have shown that phosphatidylserine-containing liposomes bind to VSV. The finding that phosphatidylserine directly binds to VSV and inhibits VSV attachment and infectivity suggests that plasma membrane phosphatidylserine could function as a binding site or portion of a binding site for VSV.
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PMID:Inhibition of VSV binding and infectivity by phosphatidylserine: is phosphatidylserine a VSV-binding site? 629 4

The thiophospholipid 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC) was shown to be a mixture of two diastereomers by 31P nuclear magnetic resonance. The isomer that resonates at the lower field in CDCl3 (56.12 ppm) was designated as isomer A and the other (resonates at 56.07 ppm) as isomer B. Phospholipase A2 from four different sources (bee venom, Naja naja venom, Crotalus adamanteus venom, and porcine pancreas) was shown to hydrolyze the isomer B of DPPsC specifically, whereas phospholipase C from two different sources (Bacillus cereus and Clostridium perfringens) hydrolyzes isomer A specifically. So that the two diastereomers could be separated, DPPsC(A + B) was first digested with phospholipase A2 to give 1-palmitoyl-sn-glycero-3-thiophosphocholine (MPPsC) (which is designated as isomer B of MPPsC) and the unreacted DPPsC(A). Reacylation of MPPsC(B) gave pure DPPsC(B). The properties of DPPsC(A) and DPPsC(B) were investigated by 31P, 13C, 1H, and 14N nuclear magnetic resonance (NMR). 1H and 13C NMR showed that both isomers in methanol solution have conformational properties similar to those of the natural phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. On the other hand, the two isomers A and B showed small but significant differences in the chemical shifts of the carbon in the chiral carbon center and the phosphorus in the chiral phosphorus center.
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PMID:Phospholipids chiral at phosphorus. Preparation and spectral properties of chiral thiophospholipids. 668 28

Brush-border membrane vesicles prepared from rabbit kidney cortex were incubated at 37 degrees C for 30 min with phosphatidylinositol-specific phospholipase C. This maneuver resulted in a release of approx. 85% of the brush-border membrane-linked enzyme alkaline phosphatase as determined by its enzymatic activity. Transport of inorganic [32P]phosphate (100 microM) by the PI-specific phospholipase C-treated brush-border membrane vesicles was measured at 20-22 degrees C in the presence of an inwardly directed 100 mM Na+ gradient. Neither initial uptake rates, as estimated from 10-s uptake values (103.5 +/- 6.8%, n = 7 experiments), nor equilibrium uptake values, measured after 2 h (102 +/- 3.4%) were different from controls (100%). Control and PI-specific phospholipase C-treated brush-border membrane vesicles were extracted with chloroform/methanol to obtain a proteolipid fraction which has been shown to bind Pi with high affinity and specificity (Kessler, R.J., Vaughn, D.A. and Fanestil, D.D. (1982) J. Biol. Chem. 257, 14311-14317). Phosphate binding (at 10 microM Pi) by the extracted proteolipid was measured. No significant difference in binding was observed between the two types of preparations: 31.0 +/- 9.37 in controls and 29.8 +/- 8.3 nmol/mg protein in the proteolipid extracted from PI-specific phospholipase C-treated brush-border membrane vesicles. It appears therefore that alkaline phosphatase activity is essential neither for Pi transport by brush-border membrane vesicles nor for Pi binding by proteolipid extracted from brush-border membrane. These results dissociate alkaline phosphatase activity, but not brush-border membrane vesicle transport of phosphate, from phosphate binding by proteolipid.
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PMID:Enzymatic removal of alkaline phosphatase from renal brush-border membranes. Effect on phosphate transport and on phosphate binding. 669 85

Hemolysis by leptospiral hemolysin was strongly inhibited by bovine serum. The inhibitory activity was observed in the chloroform-methanol-soluble fraction of bovine serum. The inhibitor was eluted in a complex lipid fraction and was separated into two fractions (Fr. I and II) by silicic acid column chromatography. Fractions I and II inhibited approximately 75% and 95%, respectively, of hemolysis by leptospiral hemolysin. Fraction I was identified as phosphatidylethanolamine (PdE) by silica gel thin-layer chromatography (TLC). Two kinds of phospholipids (PLs) were detected in Fr. II by TLC. One was resistant to alkaline treatment and was identified as sphingomyelin (Spm), and the other was sensitive to such treatment and was identified as phosphatidylcholine (PdC). PLs, such as Spm, PdC, phosphatidylglycerol, PdE, phosphatidylserine and cardiolipin, inhibited hemolysis by leptospiral hemolysin, but phosphatidylinositol did not show any inhibitory activity. PLs lacking the amino group in the polar backbone of the molecules were more effective. From experiments using erythrocytes of various kinds of animals, it was revealed that the hemolytic sensitivity of mammalian erythrocytes to leptospiral hemolysin depended on the Spm content in the erythrocyte membrane. On the other hand, phospholipase C (PLase C) activity with Spm and PdC as substrates was detected in the culture supernatant of Leptospira. Therefore, leptospiral hemolysin was presumed to be PLase C, perhaps sphingomyelinase. The inhibitors of leptospiral hemolysin present in bovine serum were identified as PLs. PLs in bovine serum were suggested to function as inhibitors of the interaction between leptospiral hemolysin and the surface of the erythrocyte membrane.
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PMID:Characterization of inhibitor to leptospiral hemolysin present in bovine serum. 673 81


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