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)

Since mixtures of lipids alone are known to elicit membrane fusion without participation of fusion proteins, the role of viral lipids in the so-called virus-induced hemolysis and cell fusion has been investigated, using as a model the fowl plague virus (influenza A/FPV/Rostock/H7N1). The experiments were planned in a way that allowed quantitative modification of viral lipids without changing envelope glycoproteins. Under the conditions employed, cholesterol oxidase of Nocardia erythropolis and phospholipase C of Bacillus cereus were shown to completely modify their substrates in the virus without altering virus-associated hemagglutinating and neuraminidase activities. It was found with such enzyme treatment that virus-induced hemolysis and cell fusion are greatly influenced by cholesterol and phospholipids of the envelope. It became clear, that hemolysis and fusion are differently dependent on the nature of lipid components even though mediated by the same viral glycoproteins.
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PMID:Interplay between lipids and viral glycoproteins during hemolysis and fusion by influenza virus. 375 42

Excitation-contraction coupling in cardiac muscle is dependent on extracellular calcium and calcium bound to the surface of the myocardial cell. In this study, we examined the physical characteristics of calcium binding to adult guinea pig ventricular myocytes disaggregated mechanically in oxygenated tissue culture medium containing a proteinase inhibitor (aprotinin), and separated from cellular debris by Cytodex beads. Cells prepared in this manner excluded Trypan blue and showed no evidence of spontaneous contraction or contracture. Scatchard plots of calcium binding determined by continuous flow equilibrium dialysis revealed a high-affinity, low-capacity pool, Ka = 65 X 10(3) M-1 and Bt = 1.3 nmol X mg-1 and a low-affinity, high-capacity pool, Ka = 141 M-1 and Bt = 138 nmol X mg-1. The low-affinity pool was not detectable after lanthanum, trypsin or collagenase treatment or in cells prepared without aprotinin in the isolation medium. Both neuraminidase and phospholipase C reduced Bt of the low-affinity pool by one half, but only neuraminidase affected the affinity constant of this pool. Ka was increased to 516.7 M-1, similar to the apparent affinity constant for calcium binding estimated from dP/dtmax measured at several extracellular calcium concentrations (470 M-1). The results suggest that calcium bound to sarcolemmal phospholipids represents the superficial calcium involved in excitation-contraction coupling in the heart.
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PMID:Calcium binding to cardiac myocytes protected from proteolytic enzyme activity. 398 17

The effects of pH, trypsin, and phospholipase C on the topographic distribution of acidic anionic residues on human erythrocytes was investigated using colloidal iron hydroxide labeling of mounted, fixed ghost membranes. After glutaraldehyde fixation at pH 6.5-7.5, the positively charged colloidal particles were bound to the membranes in small randomly distributed clusters. The clusters of anionic sites were reversibly aggregated by incubation at pH 5.5 before fixation at the same pH. These results correlate with the distribution of intramembranous particles found by Pinto da Silva (J. Cell Biol.53:777), with the exception that the distribution of anionic sites on a majority of the fixed ghosts at pH 4.5 was aggregated instead of dispersed. The randomly distributed clusters could be nonreversibly aggregated by trypsin or phospholipase C treatment of intact ghosts before glutaraldehyde fixation. Previous glutaraldehyde fixation prevented trypsin and pH induced aggregation of the colloidal iron sites. Evidence that N-acetylneuraminic acid groups are the principal acidic residues binding colloidal iron was the elimination of greater than 85% of the colloidal iron labeling to neuraminidase-treated cell membranes. Colloidal iron binding N-acetylneuraminic acid residues may reside on membrane molecules such as glycophorin, a sialoglycoprotein which contains the majority of the N-acetylneuraminic acid found on the human erythrocyte membrane.
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PMID:Anionic sites of human erythrocyte membranes. I. Effects of trypsin, phospholipase C, and pH on the topography of bound positively charged colloidal particles. 412 Dec 89

Fixation of embryonic chick cells (heart, neural retina, and limb bud) in the presence of lanthanum ions shows the presence of an electron-opaque layer, about 50 A thick, external to the cell membrane. This layer, designated LSM (for lanthanum-staining material), is not removable by trypsin, pronase, EDTA, DNase, alpha-amylase, neuraminidase, or N-acetyl-L-cysteine. However, phospholipase C, in concentrations as low as 0.001 mg/ml, succeeds in stripping the LSM from the cell surface. Heating the enzyme preparation does not inhibit this activity, but removal of divalent cations does; both of these results are consistent with the known properties of phospholipase C. The LSM is present at the cell surface in the control tissues and on cells dissociated from the tissues by proteolytic enzymes and EDTA. These results are interpreted to mean that the LSM is probably an integral part of the cell and not an extraneous coat. How this phenomenon bears on the problem of cellular adhesion is discussed, as is the possible chemical composition of the LSM.
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PMID:The removal by phospholipase C of a layer of lanthanum-staining material external to the cell membrane in embryonic chick cells. 416 2

Australia antigen [Au(1)], a particle associated with viral hepatitis, was isolated from the plasma of a patient with chronic anicteric hepatitis and leukemia who had received radioactive phosphorus. We have found that the immunoreactivity and appearance of Au(1) in the electron microscope were not altered by treatment with enzymes including trypsin, pronase, lipase, phospholipase C, ribonuclease, deoxyribonuclease, amylase, and neuraminidase. In contrast, other serum constituents were degraded by these enzymes. Therefore, treatment of the patient's plasma with many enzymes was exploited as an initial step for the isolation of Au(1). Subsequently, Au(1) was purified from the enzyme-treated (32)P-labeled plasma by gel filtration through Sephadex G-200 and centrifugation through sucrose and in cesium chloride gradients. There were no detectable human serum components in the purest fractions, as tested by immunoelectrophoresis and immunodiffusion. The density of the purified Au(1) was 1.21 in CsCl. The particle measured about 200 A in diameter, was predominantly spherical in shape and appeared to be composed of subunits. Nucleic acids were not detected by spectrophotometric, radiochemical, and chemical analyses. Immunoreactivity of purified Au(1) was destroyed by heating for 1 hr at 85 degrees C but was stable at 56 degrees C. Treatment with Carnoy's solution (3 parts ethanol:1 part glacial acetic acid) followed by pronase disrupted the particles as seen with the electron microscope. These findings, combined with other published information on Australia antigen and viral hepatitis, suggest that the bulk of Australia antigen in the blood of this patient is an incomplete virus or virus capsid.
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PMID:Australia antigen (a hepatitis-associated antigen): purification and physical properties. 424 40

Broth cultures of Clostridium perfringens (ATCC 10543) were fractionated by ammonium sulfate precipitation and Sephadex G-150 chromatography. Components isolated, as well as some enzymes present in the culture, were assayed for toxicity by feeding to white mice. Early work indicated that when a meat-fat-starch slurry, infected with C. perfringens, was fed to mice, the intestinal passage time was reduced. By using large numbers of mice as test animals and analyzing the data statistically, we found that C. perfringens and several fractions from the culture supernatant significantly affected the mice. A toxic material present in the supernatant was not identifiable as phospholipase C. Phospholipase C and physphorylcholine affected the intestinal passage time of the mice only when large amounts were given. The enzyme, neuraminidase, and another unidentified compound present in the supernatant affected the passage time when very small amounts were fed to mice.
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PMID:Response of white mice to cells and culture constituents of Clostridium perfringens. 430 35

The structure and function of the platelet surface was probed by phospholipase C (Clostridium perfringens) which hydrolyzes membrane phospholipids, particularly phosphatidylcholine. Platelet phospholipids were susceptible to phospholipase C, and extent of hydrolysis was dependent on concentration of phospholipase C and Ca(++). Phospholipase C (0.15 U/ml) with Ca(++) (0.55 mM) hydrolyzed 15.6% phospholipids during 5 min. Phospholipase C released platelet serotonin (5HT), ADP, and platelet factor 4. Hydrolysis of 5% phospholipids resulted in release of 70% 5HT. Platelet 5HT release was rapid, occurring within 2 min. Phospholipase C (0.2 U/ml) with Ca(++) (0.55 mM) also released 10.35 nmol sotrage pool ADP/10(9) platelets and 63% platelet factor 4 during 3 min. Phospholipase C did not cause leakage of cytoplasmic metabolic pool ADP, since only 6.6% [(3)H]ADP was released. Ultrastructural analysis of phospholipase C-modified platelets showed that platelets were intact. After 2% phospholipid hydrolysis, centralization of granules and contraction of microtubules were evident. After 18% phospholipid hydrolysis, there were morphological indications of degranulation. Phospholipase C-induced phospholipid hydrolysis caused the release of ADP and 5HT since: (a) Phospholipase C purified by heating was shown to be free of protease and neuraminidase activity and capable of inducing the platelet release reaction. (b) Antitoxin (Cl. perfringens) neutralized phospholipase C-induced 5HT release which rules out a contaminant. (c) Phosphorylcholine, the hydrolysis product, did not induce platelet 5HT release. This study demonstrates that minimal hydrolysis of platelet phospholipids triggers the release reaction. Our hypothesis is that phospholipids, presumably phosphatidylcholine, are situated at or near active site or "receptor" on the platelet surface and function as the modulator for the release reaction.
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PMID:The role of platelet membrane phospholipids in the platelet release reaction. 437 63

Leukocytes can generate procoagulant (tissue factor) activity when incubated with endotoxin. These studies were undertaken to determine whether platelets could influence the procoagulant activity generated by leukocytes. Intact or disrupted platelets (rabbit or human) enhanced the clot-promoting properties of rabbit leukocytes. The enhancing effect of human platelets on human leukocytes required the presence of human serum (devoid of factor VII and X activities). When platelets were incubated with endotoxin in the absence of leukocytes, no increase in their clot-promoting properties was discernible. However, a mixture of platelets, leukocytes, and endotoxin generated procoagulant activity which appeared rapidly and was fivefold greater than that produced by leukocytes incubated with endotoxin alone. The enhancement produced by platelets was even more pronounced if homogenates were used. The platelet effect was examined in more detail by the substitution of membranes, granules, and the "soluble" fraction for whole platelets in the test system. The stimulating activity was localized to the particulate fractions, i.e., membranes and granules. Prior treatment of platelet membranes with phospholipase C or gangliosides or by extraction of lipid resulted in loss of enhancing activity, whereas no inhibition was observed after exposure to neuraminidase or trypsin. It is proposed that platelets contribute a membrane lipoprotein surface which enhances the procoagulant activity generated by leukocytes in the presence of endotoxin. This mechanism may be involved in some of the clinical and pathologic manifestations of gram-negative sepsis with disseminated intravascular coagulation.
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PMID:The stimulatory effect of platelets and platelet membranes on the procoagulant activity of leukocytes. 461 59

Phospholipase C (EC 3.1.4.3.) from Clostridium perfringens (crude extracts) was used to study the role of phospholipids in the osmotic permeability of the urinary bladder of the toad. When added to the serosal bath (430 mU/ml) it inhibited the effects of antidiurectic hormone (ADH) and exogenous cyclic AMP. Under the same conditions the increase in osmotic flow produced by serosal hypertonicity (SH) was slightly enhanced by the lipase. The hydroosmotic effect of SH was greatly potentiated by the lipase by decreasing 10-fold the Ca2+ concentration. The SH-induced flow was inhibited by the lipase if the Ca2+ or the H+ concentration was increased 10-fold, but not if the increase in positive charges was produced by a concentration of Mg2+. Phospholipase C had no effect on the action of either ADH or SH if added to the mucosal bath. Serosal neuraminidase or phospholipase A2 could not mimic the effect of phospholipase C on SH. The effect of phospholipase C on the response to SH was not modified if fatty acid-free bovine serum albumin was added to the bath. Therefore, the release of products of lipolysis into the bath do not seem to be responsible for the effects of phospholipase C on SH-induced water flow. The results suggest that the effects of the enzyme on the composition and rearrangement of lipids at the basolateral membrane produce modifications of the water flow. Ca2+ and H+ may modify the enzyme-substrate interaction, suggesting that different phospholipids may be differentially involved in the control of water permeability of the basolateral membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ca2+- and H+-dependent effects of crude bacterial phospholipase C on the hydroosmotic response of toad urinary bladder to serosal hypertonicity. 608 40

[3H]prostaglandin E2 (PGE2) binding receptors exist in rabbit alveolar bone cell membranes. The presence of high (Kd = 3.9 X 10(-9) M) and low (Kd = 8.8 X 10(-8) M) affinity binding sites of [3H]PGE2 was demonstrated. The saturation values of [3H]PGE2 for high and low affinity binding sites were 0.13 pmol/mg protein and 1.22 pmol/mg protein, respectively. The digestion of the membranes with pronase, phospholipase C, D and neuraminidase led to a decrease of [3H]PGE2 binding but phospholipase A2 did not.
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PMID:Some properties of prostaglandin E2 receptors in rabbit alveolar bone cell membranes. 613 25


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