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)

Two murine monoclonal antibodies have been produced which identify a novel surface antigen expressed on human leucocytes in a non-lineage-restricted distribution. Antibodies WM-63 and WM-68 were derived after immunization of mice with human T-CLL cells and the leukaemic cell line HSB-2. Both antibodies were shown to react with over 90 per cent of normal T and B lymphocytes from peripheral blood and tonsil, and also with monocytes from peripheral blood. A subset of bone marrow leucocytes, including granulocyte-macrophage progenitors, were also reactive. No activity with non-haemopoietic cells or tissues could be identified, however WM-63 and WM-68 showed binding to virtually all cases of chronic B cell malignancy, including chronic lymphatic leukaemia and non-Hodgkin's lymphoma, as well as a proportion of cases of acute leukaemia. Although the antigen recognized by these antibodies could not be immunoprecipitated from membrane extracts, it was removed from the surface of intact cells using the proteolytic enzymes protease and papain. Re-expression on cultured cells was inhibited by incubation with puromycin, cycloheximide, and tunicamycin, indicating that the epitopes detected by WM-63 and WM-68 are likely to be carbohydrate moieties on a protein backbone. Removal of the antigen from the cell surface by treatment with the enzyme phosphatidyl-inositol phospholipase C indicates that it is linked by a phosphatidyl-inositol bond. WM-63 and WM-68 were both recently clustered at the Fourth International Workshop on Human Leucocyte Differentiation Antigens into CD-48, together with four other monoclonal antibodies. Although no biological function has been ascribed to the molecule detected by these antibodies, its restriction to the haemopoietic lineage suggests a role in regulation of leucocyte function.
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PMID:A novel non-lineage antigen on human leucocytes: characterization with two CD-48 monoclonal antibodies. 208 34

After culturing mouse peritoneal cells in vitro for 4 days, high numbers of cells can be detected that secrete autoantibodies against isologous red blood cells (RBC), modified with the proteolytic enzyme bromelain (Brom). Plaque-forming cell numbers against mouse Brom RBC were significantly reduced by pretreating mouse Brom RBC prior to haemolytic assay with phospholipase C, an enzyme that hydrolyzes phospholipids, notably phosphatidylcholine. In contrast, further treatment of mouse Brom RBC with Brom, neuraminidase, beta-chymotrypsin, trypsin, or papain had no effect on plaque-forming cell numbers. These results show that phosphatidylcholine is an integral part of the mouse RBC autoantigen exposed by Brom treatment.
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PMID:Mouse autoantibodies bind to a phospholipase-C-sensitive structure on red blood cells. 217 39

Membrane-associated decay accelerating factor (DAF) of human erythrocytes (Ehu) was analyzed for a C-terminal glycolipid anchoring structure. Automated amino acid analysis of DAF following reductive radiomethylation revealed ethanolamine and glucosamine residues in proportions identical with those present in the Ehu acetylcholinesterase (AChE) anchor. Cleavage of radiomethylated 70-kilodalton (kDa) DAF with papain released the labeled ethanolamine and glucosamine and generated 61- and 55-kDa DAF products that retained all labeled Lys and labeled N-terminal Asp. Incubation of intact Ehu with phosphatidylinositol-specific phospholipase C (PI-PLC), which cleaves the anchors in trypanosome membrane form variant surface glycoproteins (mfVSGs) and murine thymocyte Thy-1 antigen, released 15% of the cell-associated DAF antigen. The released 67-kDa PI-PLC DAF derivative retained its ability to decay the classical C3 convertase C4b2a but was unable to membrane-incorporate and displayed physicochemical properties similar to urine DAF, a hydrophilic DAF form that can be isolated from urine. Nitrous acid deamination cleavage of Ehu DAF at glucosamine following labeling with the lipophilic photoreagent 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine ([125I]TID) released the [125I]TID label in a parallel fashion as from [125I]TID-labeled AChE. Biosynthetic labeling of HeLa cells with [3H]ethanolamine resulted in rapid 3H incorporation into both 48-kDa pro-DAF and 72-kDa mature epithelial cell DAF. Our findings indicate that DAF and AChE are anchored in Ehu by the same or a similar glycolipid structure and that, like VSGs, this structure is incorporated into DAF early in DAF biosynthesis prior to processing of pro-DAF in the Golgi.
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PMID:Decay accelerating factor of complement is anchored to cells by a C-terminal glycolipid. 243 21

Decay-accelerating factor (DAF) of human erythrocytes is a glycoprotein with a Mr of 65,000 that is anchored in the membrane via a glycolipid tail. During the purification of DAF, two lower m.w. forms were noted. DAF-A had an Mr of 63,000, and DAF-B had an Mr of 55,000. In a fluid phase assay, both forms accelerated the decay of the classical and the alternative C3 convertases with a specific activity similar to that of DAF. However, the decay-accelerating activity for the cell-bound C3 convertases was abolished, suggesting that neither could insert into E membranes and therefore that the glycolipid tail is altered. Analysis by molecular sieve high-pressure liquid chromatography demonstrated that DAF-A eluted with a Mr of approximately 450,000, similar to native DAF, and was thus in an aggregated form. In contrast, DAF-B eluted as a monomer with a Mr of approximately 60,000. DAF-A, but not DAF-B, bound to a hydrophobic column. To further characterize these two forms, surface-labeled human erythrocytes were incubated with phosphatidyl inositol-specific phospholipase C or papain. The phospholipase inefficiently released a form of DAF that was slightly larger (Mr of 64,000) than DAF-A. Papain efficiently released a 55,000 fragment that had the same Mr as DAF-B. To determine if DAF was cleaved by endogenous enzymes, surface-labeled erythrocytes were incubated with leukocytes. The kinetics of the leukocyte-induced degradation was similar to those observed with papain, and the released fragment aligned on seizing gels with the papain-derived fragment. We hypothesize that endogenous phospholipases and proteases cleave DAF to produce fragments similar to DAF-A and DAF-B, respectively.
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PMID:Additional forms of human decay-accelerating factor (DAF). 244 Sep 50

Serine protease inhibitors with a specificity for trypsin inhibit interferon-gamma (INF-gamma)-induced HLA-DR expression on a hybrid human epidermal cell line (H12), dermal fibroblasts, and primary keratinocytes. Protease inhibitors with a specificity for chymotrypsin or papain fail to inhibit IFN-gamma. The inhibitory effect of the trypsin inhibitors is similar to that of glucocorticoids in that it is a transient event, fading with length of exposure to IFN-gamma, and is reversed by the addition of dibutyryl cyclic AMP (dbcAMP) and phospholipase C(PLC) from Clostridium perfringens. In H12 cells, dbcAMP and PLC enhance the IFN-gamma induction of HLA-DR, but do not induce in the absence of INF-gamma. Evidence suggests that the protease inhibitors, as well as dbcAMP and PLC, may modulate HLA-DR expression at a post-translational site as well as during IFN-gamma signal transduction. These results suggest that trypsin-like protease activity may be required for cellular HLA-DR antigen expression following exposure to IFN-gamma.
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PMID:Trypsin inhibitors inhibit induction by interferon-gamma of HLA-DR antigen expression on human skin cells. 247 85

In the present investigation we compared the glycoprotein DPP IV from rat liver and Morris hepatoma 7777 by means of biochemical and immunological methods. For that purpose nine monoclonal anti-DPP IV-antibodies recognizing four different epitopes and a monospecific anti-DPP IV-antiserum were applied. In the homogenates of both tissues a plasma membrane-bound and a soluble form were detected. The immunological cross-reactivity of both forms was demonstrated with the antiserum and the monoclonal antibodies against the epitopes A, B and C while epitope D was restricted to liver plasma membrane. Differences of the distinct DPP IV forms were exhibited in the molecular weights, isoelectric points and peptide maps. In the hepatoma homogenate only 10% of DPP IV activity was found compared to normal liver but the ratio of soluble to membrane-bound form is higher in the hepatoma than in the liver. The fractionation of the homogenates into different cell components revealed for the liver a continuous increase of DPP IV activity from the endoplasmic reticulum fractions to the Golgi apparatus and finally to the plasma membranes. By contrast, in hepatoma the flow from the Golgi apparatus to plasma membrane was greatly reduced. The loss of DPP IV from the surface of cultured hepatoma cells was concomitant with a decrease of cell-substratum adhesion. DPP IV was found to be inserted into the liver plasma membrane by two different mechanisms, a phospholipase C-sensitive and a papain-sensitive one. In the hepatoma the phospholipase C-sensitive anchorage was not expressed. Besides liver and hepatoma the distribution of DPP IV was characterized in various rat organs by enzyme activity, histochemistry and immunohistochemistry with the anti-DPP IV-antibodies.
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PMID:Biochemical properties of dipeptidyl peptidase IV in liver and hepatoma plasma membranes. 248 27

Incubation of radiolabeled L-glutamic acid, a putative central excitatory neurotransmitter, in 50 mM Tris-acetate buffer (pH 7.4) at 30 degrees C in the absence of brain synaptic membranes resulted in a significant adsorption of the radioactivity to glass fiber filters routinely employed to trap the bound ligand in receptor binding assays. The adsorption was not only eliminated by the inclusion of L-isomers of structurally related amino acids, but also inhibited by that of most presumed agonists and antagonists for the brain glutamate receptors. This displaceable adsorption was a temperature-dependent nonreversible, and saturable phenomenon. Scatchard analysis of these data revealed that the adsorption consisted of a single component with an apparent dissociation constant of 73 nM. The displaceable adsorption was significantly attenuated by a concurrent incubation with papain, pronase E, and phospholipase C. A significant amount of the radioactivity was detected in the pass-through fraction of the Dowex column following an application of the reaction mixture incubated with purified [3H]glutamate at 30 degrees C for 60 min in the absence of membranous proteins added. Complete abolition of the displaceable adsorption resulted from the use of incubation buffer boiled at 100 degrees C as well as filtered through a nitrocellulose membrane filter with a pore size of 0.45 micron immediately before use. These results suggest that the displaceable adsorption may be attributable to the radioactive metabolite of [3H]glutamate by microorganisms contaminating the Tris-acetate buffer. This might in part contribute to some of the controversial results with regard to receptor binding studies on acidic amino acids.
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PMID:Microbial methodological artifacts in [3H]glutamate receptor binding assays. 254 31

Bacillus thuringiensis serovar, thuringiensis (HD-2) demonstrated antibacterial activity against 48 of 56 strains of B. thuringiensis and against some other Gram-positive species but not against Gram-negative species. The antibacterial activity was not inducible by mitomycin C or by ultraviolet irradiation, and additional activity was not liberated from cells by sonication. Upon dilution of the antibacterial substance, zones of inhibition diminished without the appearance of plaques. Gel filtration chromatography indicated an Mr greater than 950,000 for the bacteriocin (thuricin) in its native form. The native thuricin was sedimented by ultracentrifugation, but electron microscopy of the pellet failed to reveal phage particles or phage components. Nondenaturing polyacrylamide gel electrophoresis (PAGE) of thuricin demonstrated the association of bacteriocin activity with a protein band which migrated only slightly into a 5% gel. Sodium dodecyl sulfate (SDS)-PAGE of partially purified thuricin revealed five major bands. Thuricin activity was substantially reduced by treatment with chymotrypsin, pronase, subtilisin, trypsin, and heat at 96 degrees C but not by treatment with lysozyme, phospholipase C, papain, peptidase, or organic solvents. It exhibited a bactericidal and bacteriolytic effect on a sensitive strain, B. thuringiensis serovar, canadensis (MF4). Partially purified preparations of thuricin had phospholipase A activity which was adsorbed by sensitive cells but not by cells which were insensitive to thuricin. Antibacterial activity was blocked by preincubation of thuricin with phospholipid. Loss of a 150-mDa plasmid was correlated with loss of thuricin production.
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PMID:Thuricin: the bacteriocin produced by Bacillus thuringiensis. 272 45

The larval midgut epithelial cell of the silkworm, Bombyx mori, has two forms of alkaline phosphatase and trehalase, soluble and membrane-bound. Alkaline phosphatase and trehalase of the latter form are found in the brush border membrane and the basolateral membrane, respectively. In this work we studied the membrane anchors of these membrane-bound enzymes. Alkaline phosphatase was solubilized by phosphatidyl-inositol-specific phospholipase C, but not by papain. Conversely, trehalase was released from the membrane by papain, but not by phosphatidylinositol-specific phospholipase C. Both enzymes were solubilized in an amphiphilic form with 0.5% Triton X-100 plus 0.5% sodium deoxycholate (pH 7.0). The detergent-solubilized alkaline phosphatase and trehalase were converted to hydrophilic form on incubation with phosphatidylinositol-specific phospholipase C and papain, respectively. The effects of papain on solubilization and conversion of trehalase were completely inhibited by leupeptin. These results suggest that, in the silkworm larvae, alkaline phosphatase is anchored in the brush-border membrane via a glycosyl-phosphatidylinositol, while trehalase is associated with the basolateral membrane through a hydrophobic segment of the polypeptide.
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PMID:Membrane anchors of alkaline phosphatase and trehalase associated with the plasma membrane of larval midgut epithelial cells of the silkworm, Bombyx mori. 276 26

Transmissible gastroenteritis virus was readily adsorbed onto chicken erythrocytes at 4 degrees C. The hemagglutinin thus adsorbed could be eluted from the erythrocytes by incubating in phosphate buffered saline at 37 degrees C. The receptor on chicken erythrocytes for the hemagglutinin was inactivated by neuraminidase and potassium periodate, but not by trypsin, 2-mercaptoethanol and formalin. The hemagglutinin was inactivated by trypsin, papain, pepsin, alpha-amylase, phospholipase C, neuraminidase, formalin, 2-mercaptoethanol, potassium periodate, ethyl ether, chloroform, Tween-80 and beta-propiolactone, but not by sodium deoxycholate and trichlorotrifluoroethane, suggesting that the active component of the hemagglutinin involved glycoproteins. The hemagglutinin was stable at 37 degrees C or lower temperatures but not at 60 degrees C or higher temperatures. The hemagglutinin activity was resistant to ultraviolet irradiation, while the infectivity was very susceptible. The hemagglutinin and the infectivity were readily sedimented by ultracentrifugation at 45,000 x g for 60 minutes. In rate zonal centrifugation of the hemagglutinin preparation on a sucrose density gradient, the hemagglutinin activity showed a sharp peak at 1.19 g/ml coinciding with the peak of infectivity. The activity in the peak fraction seemed to be structurally associated with virus particles.
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PMID:Physicochemical properties of transmissible gastroenteritis virus hemagglutinin. 283 45


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