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)

Apparent values of Km and Vmax have been measured for catalysis of hydrolysis of unsonicated egg lecithin liposomes, activated through addition of 0.4 M n-hexanol, by phospholipases A2 from bee and snake venoms and by phospholipase C from Clostridium welchii as a function of the concentration of three surfactants: hexadecylamine, hexadecyltrimethylammonium bromide, and dihexadecyl phosphate. For all three enzymes, values of Km and Vmax show little or no dependence on the concentration of these ionic surfactants, demonstrating that the liposomal surface charge is not a crucial factor in determining susceptibility to phospholipase-catalyzed hydrolysis.
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PMID:Phospholipases. III. Effects of ionic surfactants on the phospholipase-catalyzed hydrolysis of unsonicated egg lecithin liposomes. 0 May 6

The latency of inosine-5'-diphosphatase has been studied in microsomes isolated from rat liver. The appearance of latent activity was the result of an increase in the Vmax of the enzyme. This was observed when assays were carried out in the presence of sodium deoxycholate, after microsomes were treated wtih phospholipase C, or at pH 10.3 and after microsomes were subjected to nitrogen cavitation. The apparent Km of inosine-5'-diphosphatase for IDP was unchanged when microsomes were treated with phospholipase C or at pH 10.3 after both these treatments approximately 85% of the enzyme remained bound to the membrane. In contrast, when microsomes were treated with phospholipase C or at pH 10.3 after both these treatments approximately 85% of the enzyme remained bound to the membrane. In contrast, when microsomes were treated with sodium deoxycholate or subjected to nitrogen cavitation, approximately 75% of the inosine-5'-diphosphatase activity was released from the membrane, and the apparent Km of the enzyme for IDP increased 4- and 2-fold, respectively. Microsomal cisternae were loaded with lead phosphate by incubation with glucose-6-P and Pb2+, and the release of this lead phosphate following the addition of EDTA to the medium was determined to estimate the permeability of the microsomal membrane. When microsomes were treated with sodium deoxycholate, phospholipase C, or at alkaline pH, the microsomal membrane became almost completely permeable to EDTA under conditions where there was little or no increase in the activity of inosine-5'-diphosphatase. Microsomes were treated at pH 10.3 and then adjusted slowly to pH 7.5. The activity of inosine-5'-diphosphatase decreased to the same activity observed in untreated preparations. The results seem of exclude the possibility that latent inosine-5'-diphosphatase activity is the result of an increased permeability of the membrane to IDP. They are, however, consistent with the presence of a noncompetitive inhibitor of the enzyme in the microsomal membrane.
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PMID:Latency of inosine-5'-diphosphatase in microsomes isolated from rat liver. 1 80

Lipid micelles were prepared by incubating a mixture of glycerides (triolein, diolein, and monoolein), and lecithin in Krebs-Ringer phosphate buffer at 37 degrees C for 30 min. It was found that adrenaline stimulated the release of free fatty acids in a lipolytic system consisting of the lipid micelles and adipose tissue lipase. Adrenaline did not increase the cyclic AMP content of the reaction mixture. Dibutyryl cyclic AMP, theophylline, and phospholipase C increased the rate of lipolysis in the system but cyclic AMP and phospholipase D did not.
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PMID:Studies on adrenaline-induced lipolysis in artificial lipid micelles. 1 41

The conditions necessary for the secretion of phospholipase C (phosphatidylcholine cholinephosphohydrolase) by Pseudomonas aeruginosa were studied. Enzyme secretion by washed cell suspensions required a carbon source and ammonium, potassium, and calcium ions. The calcium requirement could be substituted by magnesium and strontium but not by copper, manganese, cobalt, or zinc. During growth in liquid medium, cells secreted phospholipase C during late logarithmic and early stationary phases. Secretion was repressed by the addition of inorganic phosphate but not by organic phosphates, glucose, or sodium succinate. Studies with tetracycline indicated that de novo protein synthesis was necessary for the secretion of phospholipase C and that the exoenzyme was not released from a preformed periplasmic pool. Similarly, extraction of actively secreting cells with 0.2 M MgCl2 at pH 8.4 solubilized large quantities of the periplasmic enzyme alkaline phosphatase but insignificant amounts of phospholipase C. Bacteria continued to secrete enzyme for nearly 45 min after the addition of inorganic phosphate or rifampin.
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PMID:Secretion of phospholipase C by Pseudomonas aeruginosa. 11 87

1. Pretreatment of frozon cryostat sections with formaldehyde or calcium ions inhibits diffusion of the plasma membrane enzymes 5' nucleotidase, ATP-ase and alkaline phosphatase during incubation. 2. Treatment of fixed sections with different kinds of buffer at 37 degrees C induces diffusion of enzyme activity from the plasma membrane to other sites of the section and into the incubation medium. This buffer influence depends on temperature: at 4 degrees C only a slight diffusion occurs. Addition of phospholipase C, digitonin or taurocholate to the buffer opposes the buffer effect. 3. Pretreatment of frozen cryostat sections with a mixture of equal parts of chloroform and acetone give a good fixation of the plasma membrane enzymes 5'-nucleotidase, ATP-ase, alkaline phosphate and leucyl-beta-naphthylamidase. During this treatment the different kinds of lipids present in the membrane are ex-racted equally. After this fixation buffer treatment does not cause a visible diffusion of enzyme activity in the section. Only a slight diffusion (1 till 7 percent) into the buffer solution takes place. 4. The mentioned treatments open up possibilities to get insight into the membrane anchorage of plasma membrane enzymes.
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PMID:Influence of fixation and buffer treatment on the release of enzymes from the plasma membrane. 14 99

Commercially available preparations of phospholipase C from Clostridium perfringens are commonly contaminated with theta haemolysin, one of a group of bacterial haemolysins called oxygen labile (O-labile) haemolysins. Treatment of erythrocyte ghosts and a mixed lipid dispersion containing cholesterol with commercially available phospholipase C in the absence of Ca-2+ and the presence of phosphate buffer and/or EDTA resulted in the formation and release of ring or arc-shaped structures. Highly purified phospholipase C, free of theta-haemolysin, produced no changes in the morphology of erythrocyte ghosts or lipid dispersions in the presence of phosphate or EDTA, but caused the formation of typical diglyceride droplets in the presence of Ca-2+ in the absence of these inhibitors. Ring structures, identical to those caused by commercial phospholipase C, were formed on addition of highly purified theta-haemolysin to erythrocyte ghost membranes, lipid dispersions containing cholesterol and cholesterol dispersions, but not on treatment of membranes from Micrococcus lysodeikticus. Heat-inactivated O-haemolysin (60 degrees C for 10 min) produced no such effects. The dimensions of rings and arcs displayed heterogeneity. The outside diameters in various preparations varied from approx. 27-58 nm with border thickness of 4.1-7.8 nm.
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PMID:Interaction of Clostridium perfringens theta-haemolysin, a contaminant of commercial phospholipase C, with erythrocyte ghost membranes and lipid dispersions. A morphological study. 16 11

1. Pure or impure C-type phospholipases hydrolysed rat liver microsomal phosphatides in situ at 5 degrees or 37 degrees C. At 5 degrees C mean hydrolysis of total phospholipids was 90% by Bacillus cereus and 75% by Clostridium perfringens (Clostridium welchii) C-type phospholipases. 2. Four degrees of inhibition of glucose 6-phosphatase (D-glucose 6-phosphate phosphohydrolase; EC 3.1.3.9) resulted. (a) At 37 degrees C inhibition was virtually complete and apparently irreversible. (b) At 5 degrees C phospholipase C inhibited 50-87% of the activity expressed by intact control microsomal fractions. (c) Bovine serum albumin present during delipidation alleviated most of this inhibition: at 5 degrees C phospholipase C plus bovine serum albumin inhibited by 0-35% (mean 18%):simultaneous stimulation by the destruction of its latency seems to offset glucose 6-phosphatase inhibition, sometimes completely. (d) If latency was first destroyed, phospholipase C plus bovine serum albumin inhibited 30-50% of total glucose 6-phosphatase activity at 5 degrees C. Only this inhibition is likely largely to reflect the lower availability of phospholipids, essential for maximal enzyme activity, as it is virtually completely reversed by added phospholipid dispersions. Co-dispersions of phosphatidylserine plus phosphatidylcholine (1:1, w/w) were especially effective but Triton X-100 was unable effectively to restore activity. 3. Considerable glucose 6-phosphatase activity survived 240min of treatment with phospholipase C at 5 degrees C, but in the absence of substrate or at physiological glucose 6-phosphate concentrations the delipidated enzyme was completely inactivated within 10min at 37 degrees C. However, 80mM-glucose 6-phosphate stabilized it and phospholipid dispersions substantially restored thermal stability. 4. It is concluded that glucose 6-phosphatase is at least partly phospholipid-dependent, and complete dependence is not excluded. For reasons discussed it is impossible yet to be certain which phospholipid class(es) the enzyme requires for activity.
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PMID:Inhibition of glucose 6-phosphatase by pure and impure C-type phospholipases. Reactivation by phospholipid dispersions and protection by serum albumin. 16 86

The specific steroid binding capacity of soluble preparations from mouse fibroblasts and rat thymic lymphocytes is inactivated by incubation with phospholipases. Receptor binding is drastically reduced by very low concentrations of boiled phospholipase A preparations from bee venom and snake venoms. The enzyme effect is calcium-dependent and is blocked by both phospholipid and a substrate analog that is a competitive inhibitor of phospholipase A. The specific binding capacity is also sensitive to digestion by phospholipase C. Two possible mechanisms are considered for the phospholipase A effect: (a) the receptor protein may be associated with a phospholipid component which is required for specific hormone binding; (b) phospholipase A may be producing detergent products that are indirectly inactivating the receptor. Examination of the effects of lysophosphatide on the receptor and assay of lipid phosphate in the receptor preparation do not support a mechanism based solely on detergent effects. Because phospholipase C, which does not produce detergent products, also inactivates the binding, we propose that the phospholipases may be digesting the phospholipid which is a requisite component of the glucocorticoid receptor.
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PMID:Evidence for a phospholipid requirement in the specific binding of glucocorticoids to receptors of fibroblasts and thymic lymphocytes. 17 9

Nascent calcium phosphate promotes the agglutination and fusion of human erythrocyte ghosts. Membrane phospholipids of erythrocyte ghosts treated with Ca2+ and phosphate ions become exposed to attack by phospholipase C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) (Bacillus cereus). Freeze-fracture pictures of fused erythrocyte ghosts show the presence of regions deficient in intramemebrane particles in the protoplasmic face which we believe to be regions of fusion. Discontinuous regions of the protoplasmic and exoplasmic faces are observed, which are apparently intermediate stages in the process of fusion. TH-in-section electron micrographs reveal deposits of calcium phosphate in areas of contact and fusion of ghosts. Ca2+ in the presence of N-[tris(hydroxymethyl)methyl]glycine (Tricine) buffer causes the formation of blebs in the membrane but does not cause changes in the intramembrane particle pattern or induce fusion. It is suggested that nascent calcium phosphate acts by forming protein-free regions of phospholipid bilayer which can fuse readily.
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PMID:Membrane ultrastructural changes during calcium phosphate-induced fusion of human erythrocyte ghosts. 32 83

1. Phospholipase C was inactivated by exposure to the three amino-group reagents, ethyl acetamidate, 2,4,6-trinitrobenzensulphonic acid and pyridoxal 5'-phosphate plus reduction. 2. Inactivation by pyridoxal 5'-phosphate showed the characteristics of Schiff's base formation with the enzyme. The pyridoxal 5'-phosphate-treated enzyme after reduction had an absorbance maximum at 325 mm and 6-N-pyridoxyl-lysine was the only fluorescent component after acid hydrolysis. 3. For complete inactivation, 2 mol of pyridoxal 5'-phosphate or 7 mol of 2,4,6-trinitrophenyl were incorporated/mol of enzyme. 4. The two apparently essential lysine residues were much more reactive to pyridoxal 5'-phosphate than the other 19 lysine residues in the enzyme. 5. Binding of phospholipase C to a substrate-based affinity gel caused marked protection against inactivation by pyridoxal 5'-phosphate. For complete inactivation of the gel-bound enzyme, 5 mol of pyridoxal 5'-phosphate were incorporated/mol of enzyme and there was no evidence of two especially reactive lysine residues. 6. On application of pyridoxal 5'-phosphate-treated enzyme (remaining activity 30% of original) to a column of the affinity gel, some material bound and some did not. The latter contained very little enzyme activity and was heavily incorporated with reagent (9.06 mol/mol of enzyme). The former had a specific activity of 34% of that of the control and contained 1.29 mol of reagent/mol of enzyme. 7. Thus phospholipase C appears to contain two lysine residues that are essential for enzyme activity, but probably not for substrate binding.
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PMID:Phospholipase C from Bacillus cereus. Evidence for essential lysine residues. 40 7


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