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)

Rat sciatic nerve cytosol contains a phosphodiesterase of the phospholipase C type that catalyzes the hydrolysis of inositol phospholipids, with preferences of phosphatidylinositol 4'-phosphate (PIP) greater than phosphatidylinositol (PI) much greater than phosphatidylinositol 4',5'-bisphosphate (PIP2), at a pH optimum of 5.5-6.0 and at maximum rates of 55, 13, and 0.7 nmol/min/mg protein, respectively. Analysis of reaction products by TLC and formate exchange chromatography shows that inositol 1,2-cyclic phosphate (83%) and diacylglycerol are the major products of PI hydrolysis. [32P]-PIP hydrolysis yields inositol bisphosphate, inositol phosphate, and inorganic phosphate, indicating the presence of phosphodiesterase, phosphomonoesterase, and/or inositol phosphate phosphatase activities in nerve cytosol. Phosphodiesterase activity is Ca2+-dependent and completely inhibited by EGTA, but phosphomonoesterase activity is independent of divalent cations or chelating agents. Phosphatidylcholine (PC) and lysophosphatidylcholine (lysoPC) inhibit PI hydrolysis. They stimulate PIP and PIP2 hydrolysis up to equimolar concentrations, but are inhibitory at higher concentrations. Both diacylglycerols and free fatty acids stimulate PI hydrolysis and counteract its inhibition by PC and lysoPC. PIP2 is a poor substrate for the cytosolic phospholipase C and strongly inhibits hydrolysis of PI. However, it enhances PIP hydrolysis up to an equimolar concentration.
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PMID:Inositol phospholipid hydrolysis by rat sciatic nerve phospholipase C. 282 95

We have studied the de novo synthesis and subsequent turnover of major docosahexaenoate-containing molecular species in frog rod outer segment (ROS) phospholipids following intravitreal injection of [2-3H]glycerol. On selected days after injection, ROS were prepared and phospholipids extracted. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) were isolated and converted to diradylglycerols with phospholipase C. Diradylglycerols were derivatized with benzoic anhydride and resolved into diacylglycerobenzoates and ether-linked glycerobenzoates. The diacylglycerobenzoates were fractionated into molecular species by HPLC, quantitated, and counted for radioactivity. Label was incorporated into ROS phospholipids by day 1 and was followed up through the eighth day. The dipolyenoic species 22:6-22:6 from PC showed a 3-5 times higher radiospecific activity than the same species from either PE or PS. In PC, the specific activities of 16:0-22:6 and 18:0-22:6 were 3-5 times lower than the specific activity of 22:6-22:6. In contrast, for PE, the specific activities of 16:0-22:6 and 18:0-22:6 were 2-5 times higher than that of 22:6-22:6. The specific activities of 18:0-22:6 and 22:6-22:6 were similar in PS. Specific activities of the docosahexaenoate-containing species began approximating an exponential decline 6-8 days postinjection and continued through the 31st day. The rate of decline was determined by calculating the half-life of each molecular species, which was used as a measure of the turnover of the species. The species 22:6-22:6-PE and 18:0-22:6-PE showed a 2-3 times slower turnover rate than the corresponding species from either PC or PS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Docosahexaenoate-containing molecular species of glycerophospholipids from frog retinal rod outer segments show different rates of biosynthesis and turnover. 297 2

Incubation of washed human sperm with [3H]- or [14C]arachidonic acid allowed a major incorporation of the label into phospholipids, provided that the final concentration of the fatty acid did not exceed 20 microM. A further challenge with calcium ionophore A23187 of spermatozoa suspended in a calcium-containing medium led to phospholipid hydrolysis, which could account for 10-12% of total cell radioactivity. Degradation products were identified as free, unconverted arachidonic acid, occurring with some diacylglycerol. Phospholipid hydrolysis was significant after 15 min of incubation and became maximal after 120 min. It was found to be calcium dependent, diacylglycerol and free arachidonate production occurring maximally at 2 mM and 5 mM CaCl2, respectively. Phosphatidylcholine and phosphatidylinositol were the most significantly degraded phospholipids after 60 min of incubation. Similar incubations conducted with 32P-labeled sperm confirmed the selective hydrolysis of phosphatidylcholine and revealed an increase production of phosphatidic acid probably due to a phosphorylation of diacylglycerol. Under the same conditions, one third of the cells remained motile and electron microscopy revealed that acrosome reaction was completed in 40% of the cells and displayed an intermediary state in 40-50% of the spermatozoa. Furthermore, a good parallelism was observed between the extent of the acrosome reaction and the extent of phospholipid hydrolysis promoted by increasing concentrations of A23187. It is concluded that calcium entry into the cells activates both a phospholipase A2 and a phospholipase C, leading to the production of substances, like lysophospholipid, diacylglycerol or phosphatidic acid, which may or may not be involved in acrosome reaction.
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PMID:Evidence for the activation of phospholipases during acrosome reaction of human sperm elicited by calcium ionophore A23187. 310 92

The role of the gastric nonwettable hydrophobic layer (surfactant) was investigated in the mucosal protection against the damage induced by ethanol in the rat. Although aluminium hydroxide inhibited the development of ethanol-produced gastric hemorrhagic lesions, it did not increase the mucosal phospholipid content. Ambroxol, a known stimulant of pulmonary surfactant production, protected the gastric mucosa against ethanol by increasing the phospholipid content. Surface-active compounds such as dimethyl polysiloxane also inhibited the development of gastric injuries caused by ethanol in a dose-dependent manner. The essential phospholipid-containing drug (Essentiale) also showed a strong and dose-dependent cytoprotective effect. Among the possible constituents of the gastric surfactant, sphingomyelin was totally ineffective. Phosphatidylcholine, phosphatidylinositol and phosphatidylglycerol were able to reduce the extent of mucosal damage in a dose-dependent manner. Gastric mucosal injuries were significantly aggravated by pretreatment with phospholipase C. In conclusion, these results suggest that either the maintenance or the strengthening or even the replacement of the gastric nonwettable hydrophobic lining between the damaging agent and the gastric mucosa may contribute to the cytoprotective mechanism of certain compounds.
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PMID:Cytoprotective role of gastric surfactant in the ethanol-produced gastric mucosal injury of the rat. 376 92

The distribution of phospholipids over outer and inner layers of the plasma membranes of Friend erythroleukemic cells (Friend cells) and mature mouse erythrocytes has been determined. The various techniques which have been applied to establish the phospholipid localization include the following: phospholipase A2, phospholipase C, and sphingomyelinase C treatment, fluorescamine labeling of phosphatidylethanolamine, and a phosphatidylcholine transfer protein mediated exchange procedure. The data obtained with these different techniques were found to be in good agreement with each other. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol were found to be distributed symmetrically over both layers of the plasma membrane of Friend cells. In contrast, sphingomyelin was found to be enriched in the outer layer of the membrane (80-85%), and phosphatidylserine appeared to be present mainly in the inner layer (80-90%). From these results, it was calculated that the outer and inner layers accounted for 46% and 54%, respectively, of the total phospholipid complement of that membrane. Analogous studies on the plasma membrane of mature mouse erythrocytes showed that the transbilayer distribution of the total phospholipid mass appeared to be the same as in the plasma membrane of the Friend cell, namely, 46% and 54% in outer and inner layers, respectively. The outer layer of this membrane contains 57% of the phosphatidylcholine, 20% of the phosphatidylethanolamine, 85% of the sphingomyelin, and 42% of the phosphatidylinositol, and none of the phosphatidylserine was present.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phospholipid localization in the plasma membrane of Friend erythroleukemic cells and mouse erythrocytes. 385 34

We have examined the effects of phospholipase C from Bacillus cereus on the extent of phospholipid hydrolysis in envelope membrane vesicles and in intact chloroplasts. When isolated envelope vesicles were incubated in presence of phospholipase C, phosphatidylcholine and phosphatidylglycerol, but not phosphatidylinositol, were totally converted into diacylglycerol if they were available to the enzyme (i.e., when the vesicles were sonicated in presence of phospholipase C). These experiments demonstrate that phospholipase C can be used to probe the availability of phosphatidylcholine and phosphatidylglycerol in the cytosolic leaflet of the outer envelope membrane from spinach chloroplasts. When isolated, purified, intact chloroplasts were incubated with low amounts of phospholipase C (0.3 U/mg chlorophyll) under very mild conditions (12 degrees C for 1 min), greater than 80% of phosphatidylcholine molecules and almost none of phosphatidylglycerol molecules were hydrolyzed. Since we have also demonstrated, by using several different methods (phase-contrast and electron microscopy, immunochemical and electrophoretic analyses) that isolated spinach chloroplasts, and especially their outer envelope membrane, remained intact after mild treatment with phospholipase C, we can conclude that there is a marked asymmetric distribution of phospholipids across the outer envelope membrane of spinach chloroplasts. Phosphatidylcholine, the major polar lipid of the outer envelope membrane, is almost entirely accessible from the cytosolic side of the membrane and therefore is probably localized in the outer leaflet of the outer envelope bilayer. On the contrary, phosphatidylglycerol, the major polar lipid in the inner envelope membrane and the thylakoids, is probably not accessible to phospholipase C from the cytosol and therefore is probably localized mostly in the inner leaflet of the outer envelope membrane and in the other chloroplast membranes.
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PMID:Localization of phosphatidylcholine in outer envelope membrane of spinach chloroplasts. 398 5

Experiments have been performed to determine if fibroblasts from patients with Duchenne muscular dystrophy (DMD) are defective in a process of membrane repair. Normal and DMD fibroblasts were treated with phospholipase C from Clostridium perfringens to degrade plasma membrane phosphatidylcholine, and then phosphatidylcholine synthesis was measured as the incorporation of [3H] choline into lipid. Phosphatidylcholine synthesis was stimulated by phospholipase C treatment to a similar extent in normal and DMD fibroblasts. The activity of CTP: phosphocholine cytidylyltransferase, the enzyme regulating phosphatidylcholine synthesis in phospholipase C-treated mammalian cells, was also stimulated to the same extent in both cell types. The subcellular location of the cytidylyltransferase was changed by phospholipase C treatment from mostly cytosolic to mostly particulate in both normal and DMD fibroblasts. It appears, therefore, that at least one type of membrane repair system functions normally in DMD fibroblasts.
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PMID:A functional membrane repair system in Duchenne muscular dystrophy fibroblasts. 608 3

Previous studies in our laboratory on the in vitro uncoating of poliovirus have shown that HeLa cell membrane contains a modifying factor which induces early modification of virus (the loss of VP4) and a stabilizing factor which protects virus against heat-induced degradation. It has now been found that membrane-modifying factor is dependent on the presence of phospholipid for activity. Modifying activity was lost after exposure of membrane (Mem) to phospholipase C. Triton X-100-solubilized modifying factor prepared from phospholipase C-treated Mem was reactivated by phospholipid. Lecithin, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin were found to exhibit a reactivating effect. Lecithin was the most effective individual phospholipid in terms of maximal reactivation. Partial purification of Triton X-100-solubilized modifying factor was achieved by concanavalin A-Sepharose chromatography. Membrane-stabilizing factor was extracted from HeLa cell membrane by solubilization with sodium deoxycholate (DOC). Some properties of DOC-solubilized stabilizing factor were studied. The solubilized stabilizing factor was inactivated by treatment with trypsin or chymotrypsin. Treatment of the solubilized stabilizing factor with certain lipid solvents, lipolytic enzymes, or lectins had no detectable effect on stabilizing activity.
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PMID:Studies on the in vitro uncoating of poliovirus. IV. Characteristics of solubilized membrane-modifying and -stabilizing factors. 631 Aug 61

The maturation-associated human B cell rosette receptor (MER) for mouse erythrocytes has been solubilized from B cells by mild trypsinization. It specifically agglutinates mouse red cells. Material with hemagglutinating activity partitioned into the lipid-soluble phase of a Folch partition of the trypsin extract was sensitive to phospholipase C and alkali, and on two-dimensional thin layer chromatography, it co-migrated principally with phosphatidylethanolamine (PE). Phosphatidylcholine, the major lipid present, was inactive. The relationship of phospholipid structure to hemagglutinating activity has been described. PE in the crude trypsin extract was associated with unidentified glycoprotein and albumin. Material containing hemagglutinating lipid bound to a wheat germ lectin-Sepharose column and was released by N-acetylglucosamine, indicating that the PE was complexed with glycoprotein. When the crude trypsin extract or eluate from the lectin column was extracted with aqueous phenol, hemagglutinin in the aqueous phase no longer bound to wheat germ lectin-Sepharose; however, albumin was greatly enriched, indicating that some of the PE exists in a complex with albumin. The molar ratio of PE to albumin was approximately 200:1. After delipidation, this albumin (in molar excess) inhibited hemagglutination by PE in the same way as a recently described subclass of serum albumin. Studies with phospholipase-treated B cells were also consistent with PE being the MER. We conclude that MER is PE, existing in a complex containing glycoprotein and a subclass of albumin. The capacity to form rosettes can be transferred to nonrosetting Raji B cells by the complex, but not pure PE, indicating that the proteins may be involved in orienting PE correctly for it to function as the MER.
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PMID:A phosphatidylethanolamine-containing complex on human B cells that mediates rosette formation with mouse erythrocytes. 660 1

The synthetic short-chain lecithins diheptanoylphosphatidylcholine and dioctanoylphosphatidylcholine solubilize cholesterol up to 10 and 18 mol %, respectively. The half-time for diheptanoylphosphatidylcholine solubilization of solid cholesterol is 80 (+/- 30) min. This is much faster than Triton X-100 micelle or egg lecithin vesicle solubilization of solid cholesterol. Both the broadening of lecithin and [4-13C]cholesterol carbon resonances by Mn2+ and the observation of surface dilution kinetics for phospholipase A2 (Naja naja naja) and phospholipase C (Bacillus cereus) hydrolysis of the lecithins indicate that the cholesterol 3 beta-hydroxyl group resides at the particle surface exposed to solvent. Analysis of lecithin 13C chemical shifts suggests that cholesterol causes the short-chain lecithin acyl chains to become slightly more trans, although to a lesser extent than it affects egg lecithin chains in liposomes. Lecithin motion as characterized by 13C T1s and line widths is unaffected by the incorporation of cholesterol. [3,4-13C2]Cholesterol line widths are 5-10-fold narrower in these mixed micelles than in egg lecithin sonicated vesicles, while T1s in the two systems are comparable. These mixed micelles serve as substrates for cholesterol oxidase (Nocardia erythropolis) with a 40-fold rate increase over comparable cholesterol concentrations in egg lecithin vesicles. Part of this rate enhancement can be understood as an increase in interfacial area available to cholesterol oxidase in the micellar systems. These studies suggest that cholesterol oxidase has a weaker affinity for interfaces than other surface active enzymes.
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PMID:Cholesterol solubilization by short-chain lecithins: characterization of mixed micelles and cholesterol oxidase activity. 694 24


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