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)

The role of phospholipids in the activity of UDP-D-galactose: D-xylose galactosyltransferase (galactosyltransferase I) from embryonic chick cartilage was investigated. Phospholipase C treatment of particulate galactosyltransferase I caused inactivation of this enzyme to the extent of 60 to 70% as well as hydrolysis of 75 to 80% of the membrane phospholipids. Addition of phospholipid restored activity to nearly control levels. The order of effectiveness of various phopholipids in reactivating phospholipase C-treated galactosyltransferase I was as follows: lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidylethanolamine, phosphatidylcholine. The effect of phospholipase A on galactosyltransferase I activity was also examined and was found to be concentration-dependent. At concentrations less than 10 mug/mg of pellet protein, phospholipase A slightly activated galactosyltransferase I. whereas at higher concentrations it inhibited the activity in a manner similar to phospholipase C. Galactosyltransferase I was activated moderately and also solubilized by treatment with Nonidet P-40 in the presence of 0.5 M KCl. Following solubilization and purification by gel filtration and affinity chromatography, galactosyltransferase I could be inactivated by detergent removal by dialysis and subsequently reactivated by addition of detergent. Neither phospholipase C treatment nor exogenous phospholipid had any significant effect on three of the other chondroitin sulfate glycosyltransferases (UDP-D-xylose: core protein xylosyltransferase, UDP-D-glucuronic acid:3-O-beta-D-galactosyl-D-galactose glucuronosyltransferase, and UDP-N-acetyl-D-galactosamine:(BlcUA-GalNAc-4-sulfate)j N-acetylgalactosaminyltransferase). On lipid analysis by thin layer chromatography, phosphatidylcholine and phosphatidylethanolamine were found to be the major phospholipids of particulate and solubilized glycosyltransferase preparations from embryonic chick cartilage, while lysopholipids of particulate and solubilized glycosyltransferase preparations from embryonic chick cartilage, while lysophosphatidylcholine and lysophosphatidylethanolamine were barely detectable components. The concentration of these specific phospholipids was diminished greatly following phospholipase C treatment.
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PMID:Biosynthesis of chondroitin sulfate. Role of phospholipids in the activity of UDP-D-galactose: D-xylose galactosyltransferase. 94 16

The effects of lipoprotein lipase, phospholipase A2 and phospholipase C on chylomicron phosphatidylcholine and triacylglycerol were studied with rat lymph chylomicrons containing phosphatidylcholine labeled with [14C]oleic acid. Lipoprotein lipase purified from bovine milk readily hydrolyzed chylomicron phosphatidylcholine to lysophosphatidylcholine and fatty acid, and triacylglycerol to monoacylglycerol, fatty acid and glycerol. The rates of hydrolysis of phosphatidylcholine and triacylglycerol increased with enzyme concentration, and both decreased when fatty-acid binding sites on albumin in the incubation medium were limited. The proportion and amount of phosphatidylcholine hydrolyzed was always less than that of triacylglycerol. Analyses of hydrolytic products showed that lipoprotein lipase cleaved the 1-acyl ester bond of phosphatidylcholine. The findings indicate that lipoprotein lipase can account for some of the phospholipase A1 activity found in postheparin plasma. Phospholipase A2 and phospholipase C hydrolyzed chylomicron phosphatidylcholine, greater than 92% in 10 min, but not triacylglycerol. The resultant phosphatidylcholine-deficient chylomicrons, which could be concentrated by ultra-centrifugation and resuspended in incubation medium, were readily depleted of triacylglycerol when incubated with lipoprotein lipase. The findings indicate that phosphatidylcholine can be removed from the surface film of chylomicrons without disrupting the particles or blocking the action of lipoprotein lipase on the core triacylglycerol.
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PMID:Hydrolysis of chylomicron phosphatidylcholine in vitro by lipoprotein lipase, phospholipase A2 and phospholipase C. 94 90

To elucidate the mode of action of AC-3579, a diazafluoranthen derivative, the effects of the drug were tested, in incubations with rat liver homogenates on three phospholipases: the endogenous microsomal phospholipase A and the exogenous phospholipases A2 and C. The rates of hydrolysis of phosphatidylcholine and phosphatidylethanolamine, the main liver phospholipids, were significantly decreased in liver of treated animals. This inhibition was more marked in experiments with exogenous phospholipase A than with phospholipase C. For phospholipid the difference observed may be due to the decrease in activity of endogenous phospholipase A in livers of treated rats. On the other hand, the addition to the incubation media of AC-3579 or of homogenates of AC-3579-treated rat livers did not modify the action of the three phospholipases on phospholipids from normal rat liver homogenates. It is concluded that AC-3579 forms with the hydrophobic moiety of the phospholipids of smooth endoplasmic reticulum a reversible complex less accessible to the activity of phospholipase A. This mechanism accounts for the decrease in phospholipid catabolism, previously observed in vivo, which leads to hypertrophy of smooth endoplasmic reticulum and to the formation of lamellate cytosomes.
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PMID:Alterations of rat liver lysosomes and somooth endoplasmic reticulum induced by the diazafluoranthen derivative AC-3579. III. Mechanism and site of action. 112 77

The action of purified phospholipases on monomolecular films of various interfacial pressures is compared with the action on erythrocyte membranes. The phospholipases which cannot hyorolyse phospholipids of the intact erythrocyte membrane, phospholipase C from Bacillus cereus, phospholipase A2 from pig pancreas and Crotalus adamanteus and phospholipase D from cabbage, can hydrolyse phospholipid monolayers at pressure below 31 dynes/cm only. The phospholipases which can hydrolyse phospholipids of the intact erythrocyte membrane, phospholipase C from Clostridium welchii phospholipase A2 from Naja naja and bee venom and sphingomyelinase from Staphylococcus aureus, can hydrolyse phospholipid monolayers at pressure above 31 dynes/cm. It is concluded that the lipid packing in the outer monolayer of the erythrocyte membrane is comparable with a lateral surface pressure between 31 and 34.8 dynes/cm.
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PMID:Relation between various phospholipase actions on human red cell membranes and the interfacial phospholipid pressure in monolayers. 117 76

AC-3579 (2-N-methylpiperazinomethyl-1,3-diazafluoranthen 1-oxide) produces in rat hepatocytes a hypertrophy of the endoplasmic reticulum. Two possibilities that can explain this phenomenon are (1) that AC-3579 inactivates the phospholipases, and (2) that an AC-3579-lipid interaction hinders the enzymic activity. To demonstrate these hypotheses, a physicochemical model of biological membrane, the lipid-water interface, has been used. Dipalmitoyl DL-alpha-phosphatidyl-choline was spread at the air-water interface, the enzymes (phospholipase A or phospholipase C) dissolved in the aqueous phase. The enzymic reaction was first studied with and without AC-3579 dissolved in the aqueous phase; no enzymic inactivation was observed. However an AC-3579-lipid complex completely inhibited the enzymic reaction in the case of phospholipase A. An explanation is given in terms of steric hindrance to the enzyme-substrate.
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PMID:Effect of a diazafluoranthen derivative on phospholipases. A study at the air-water interface. 124 72

We have examined the in vivo labeling of lipids after a single intraperitoneal injection of the carcinogen, (C14) dimethylnitrosamine, into rats. Liver was most active in incorporating (C14) methyl groups into lipids (0.91% of the injected dose) and 80% of the activity appeared in sn-3-phosphatidyl-choline. Chromatographic analysis of the products (and derivatives) formed after treatment of the (C14) phosphatidylcholine with phospholipase A2 (EC 3.1.1.4) and phospholipase C (EC 3.1.4.3) demonstrated that 89% of the radioactivity was in the choline moiety. These results indicate the transfer of methyl groups to lipids occurred via the lipid methylation pathway that converts phosphatidylethanolamine to phosphatidylcholine.
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PMID:Transfer of methyl groups from N-dimethylnitrosamine to glycerolipids in rat liver. 126 44

The cardiovascular effects of bradykinin require additional vasoactive mediators for a fully balanced response. This includes arachidonic acid (eicosatetraenoic acid) and its metabolites, the eicosanoids (prostaglandins, leukotrienes, thromboxanes, and others). Eicosanoid generation by bradykinin is started by binding of the peptide to specific B2 receptors at the plasma membrane. This initiates G-protein coupled stimulation of phospholipase C, IP3-induced increases in cytosolic Ca2+, and stimulation of protein kinase C. Arachidonic acid is liberated from membrane phospholipids primarily via Ca(2+)-induced stimulation of phospholipase A2 and converted into tissue-specific eicosanoids by enzymes in the vicinity. In vascular tissue, most of the available arachidonic acid is converted into vasodilator prostaglandins, i.e., prostacyclin (PGI2) and prostaglandin E2 (PGE2). These prostaglandins are involved in vasodilator actions of the kinins. There is also some evidence for generation of vasoconstrictor eicosanoids, such as thromboxane A2, under certain conditions. The biological significance of kinin-related prostaglandin formation becomes apparent after inhibition of kinin breakdown by ACE inhibitors. These compounds prevent generation of vasoconstrictor angiotensin II and stimulate endothelial eicosanoid formation via local kinin accumulation. There is evidence suggesting that kinin-induced prostaglandin generation contributes to anti-ischemic, inotropic, and blood pressure-lowering effects of the compounds. This also includes inhibition of polymorphonuclear leukocyte (PMN) accumulation in injured myocardial tissue, which is antagonized by PGI2-related pathways, stimulated by ACE inhibition and/or bradykinin.
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PMID:Role of prostaglandins in the cardiovascular effects of bradykinin and angiotensin-converting enzyme inhibitors. 128 33

The secretagogue effect of prolactin (PRL) on casein release by epithelial mammary cells has been previously related to stimulation of the phospholipase A2-arachidonic acid cascade. In order to determine whether other intracellular pathways are implicated in this secretagogue effect, different agents acting on protein kinase C (PKC) and phospholipase C (PLC) activity have been assessed in vitro in lactating rabbit mammary gland fragments. Phorbol ester (20 nm TPA and 1-oleoyl-2-acetyl-sn-glycerol (10 microM (OAG) stimulated newly synthesized casein secretion and potentiated the PRL secretatogue effect. However, 100 microM quercetin, 100 microM H-7 and 5 and 20 nM staurosporine did not inhibit the latter effect. Exogenous PLC did not stimulate casein secretion. PRL did not affect production of inositol phosphates (IPs) during 10 or 60 min exposure. These results show that PKC activation may increase basal levels of casein secretion, and demonstrate that PRL does not act primarily via PKC activation or by PLC activation to stimulate casein secretion.
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PMID:The possible involvement of protein kinase C(s) and inositol phosphate metabolism in the basal but not in the prolactin stimulated casein release by the lactating rabbit mammary epithelial cell. 129 81

We investigated the effects of an exogenous Type I phospholipase C (PLC) from clostridium perfringens on arachidonic acid release and prostaglandin synthesis from gastric mucosa by determining PGE2 release from organ cultured rabbit mucosal biopsies as well as PGE2 synthesis and substrate-dependent inactivation of the prostaglandin cyclooxygenase from endogenously released arachidonic acid in mucosal homogenate. PLC dose dependently stimulated PGE2 secretion from organ cultured mucosa to 145% and 245% at 0.1 and 1.0 U/ml during a 60 minute culture period. This effect was not affected by the calmodulin antagonist N-(6-aminohexyl)-1-5-chloro-1-naphthalene-sulfonamide (W-7) or the intracellular calcium chelator 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). PLC could not be substituted by phorbol-12-myristate 13-acetate (PMA), an analogue of the diacylglycerol second messenger functions. During a 15 minute preincubation of mucosal homogenate at 37 degrees C, 1mM CaCl2 stimulated PGE2 synthesis from endogenous arachidonic acid about 5-fold compared to an EDTA-control. In contrast, the residual prostaglandin synthesizing capacity, determined by incubation with excess 14C-labelled arachidonic acid, was reduced by CaCl2 to 37% of the EDTA-value. Quinacrine, an inhibitor of arachidonic acid release from phosphatidylethanolamine, reduced both the stimulation of PGE2 synthesis and the inactivation of prostaglandin cyclooxygenase. Therefore we conclude, that this Ca(2+)-effect reflects activation of the Ca-dependent phospholipase A2 (PLA2) and, as a consequence, substrate-induced inactivation of the prostaglandin cyclooxygenase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Activation of PGE2-secretion from gastric mucosa by a type I phospholipase C is mediated by a direct release of arachidonic acid. 130 34

Dopamine receptors of D2 type present on lactotroph cells are coupled to a large series of transduction mechanisms. Beside their negative coupling with adenylate cyclase, they are also coupled with potassium and calcium channels, leading to a decreased intracellular calcium concentration. In addition, D2 dopamine receptors also modulate phospholipase activities. Dopamine inhibits inositol phosphate production, through two distinct mechanisms. One of them could represent a direct negative coupling with phospholipase C. All these transduction mechanisms of the D2 dopamine receptors implicate G proteins sensitive to pertussis toxin. In contrast, these receptors are negatively coupled to phospholipase A2 through G proteins insensitive to this toxin. Both isoforms of the D2 dopamine receptor, generated by alternate splicing of a single gene, are present in lactotroph cells. After transfection in CH4C1 cells the two isoforms are coupled with adenylate cyclase while only the shortest isoform appears negatively coupled to phospholipase C. Functional D2 dopamine receptors are present in human prolactinomas. Resistance to bromocriptine therapy is associated with a decreased density of these receptors in the tumor. In addition, the ratio of the two receptor isoforms (measured by PCR) is different in responsive and resistant tumors. Furthermore, the activity of Gi/Go proteins coupled to adenylate cyclase appears also affected in resistant tumors. Resistance to bromocriptine therapy appears thus to involve multiple changes at the different levels of the multiple mechanisms of action of dopamine on lactotroph cells.
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PMID:D2 dopaminergic receptors: normal and abnormal transduction mechanisms. 130 22


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