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)

Recently we described a saturable, high-affinity binding site for vesicular stomatitis virus (VSV) on the surface of Vero cells that appears to mediate viral infectivity. To isolate this binding site, we have extracted Vero cells with the detergent, octyl-beta-D-glucopyranoside. The dialyzed detergent extract specifically inhibits the saturable, high-affinity binding of 35S-methionine-labeled VSV to Vero cells. The inhibitory activity is resistant to protease, neuraminidase and heating to 100 degrees C. It is soluble in chloroform-methanol and inactivated by phospholipase C, suggesting that it is a phospholipid. Of various purified lipids tested, only phosphatidylserine was capable of totally inhibiting the high-affinity binding of VSV. The half-maximal inhibitory concentration for phosphatidylserine was 1 microM. Phosphatidylserine also inhibited VSV plaque formation by 80%-90%; Herpes simplex virus plaque formation was unaffected. Centrifugation and electron microscopy studies have shown that phosphatidylserine-containing liposomes bind to VSV. The finding that phosphatidylserine directly binds to VSV and inhibits VSV attachment and infectivity suggests that plasma membrane phosphatidylserine could function as a binding site or portion of a binding site for VSV.
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PMID:Inhibition of VSV binding and infectivity by phosphatidylserine: is phosphatidylserine a VSV-binding site? 629 4

Sarcolemmal membranes prepared by "gas dissection" from monolayers of cultured neonatal rat heart cells were studied with respect to their ability to bind calcium. Lanthanum displacement of calcium was 168 +/- 7 nmol/mg sarcolammel protein. This represents 3.21 mmol Ca/kg dry weight original cells on the basis of the measured membrane protein: dry cell weight ratio of 19.1 g/kg. Lanthanum-displaceable calcium from whole cells was essentially equal (3.32 mmol/kg dry weight), which indicates that all calcium displaceable from whole cells by lanthanum is localized to sarcolemmal sites. The potency of a series of divalent cations for calcium displacement from the sarcolemma was according to similarity of their crystal radii to that of calcium (cadmium greater than manganese greater than magnesium). This order was the same for the cations' ability to displace calcium from whole cells and for their ability to uncouple excitation from contraction in neonatal papillary muscle. The membranes were treated with four enzymes: phospholipase A2, phospholipase C, phopholipase D, and neuraminidase. Phospholipase A2 and phospholipase D produced significantly increased calcium-binding. The increased binding secondary to phospholipase A2 treatment was eliminated by an albumin wash which was indicative of binding to the fatty acid product of hydrolysis. The increase after phospholipase D treatment can be attributed to an increase in phosphatidate, with attendant increase in net anionic charge on the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of cations, phospholipases, and neuraminidase on calcium binding to "gas-dissected" membranes from cultured cardiac cells. 631 48

Giant-cell formation induced by macrophage fusion factor (MFF) was not altered after pretreatment of macrophages with trypsin, chymotrypsin, pronase, neuraminidase, phospholipase C, or phospholipase D. Pretreatment of macrophages with either alpha-mannosidase or alpha-glucosidase completely inhibited giant-cell development, without altering macrophage viability. No alteration of giant-cell formation was observed when 0.1 M of L-fucose, N-acetyl-glucosamine, D-arabinose, D-xylose, melibiose, D-glucose, D-galactose, alpha-lactose, sucrose, D-fructose, or maltose was present during incubation of macrophages with MFF. Giant-cell formation was abolished when 0.1 M alpha-D-mannose was present during macrophage incubation with MFF. These results suggest that the protein moiety of MFF recognizes a specific receptor site on the macrophage membrane, one that is different from those described for other lymphokines and contains alpha-mannose.
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PMID:Chemical nature of the interaction between macrophage fusion factor and macrophage membranes. 635 71

The phospholipids in the membrane of the Newcastle disease virus were hydrolysed by means of the phospholipase enzyme C, whereas the infectious titer of the virus did not change, however its neuraminidase activity dropped. It was found that sphingomyelin in conc. of 250 micrograms/cm3 or lipids of the Newcastle disease virus membrane added to phospholipase C-treated hemagglutinin-neuraminidase restored its activity. The phospholipid 'phosphatidiletanolamine' could not restore the activity of the virus neuraminidase.
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PMID:[Restoration of the biological activity of hemagglutinin--neuraminidase in NDV with phospholipids]. 652 78

Removal of up to 50% of the sialic acid from aggregates of 7-day chick embryo heart cells during incubation in a highly purified preparation of neuraminidase resulted in hyperpolarization of the maximum diastolic potential, reduction in the slope of diastolic depolarization leading to slowing of beating, negative shifts of threshold potential and the voltage at which upstroke velocity was maximal, and an initial increase in the action potential overshoot. These effects were opposite to those induced by phospholipase C, a possible contaminant. The modification of electrical properties by neuraminidase is suggested to result from an enhanced influx of calcium ions that might "screen" or bind specifically to internal negative fixed charges and thereby shift the voltage dependence of conductance and kinetic parameters to more negative potentials. This hypothesis is supported by the results above and by greater uptake of 45Ca following release of sialic acid, augmentation of enzyme-induced changes in elevated Ca2+, and the similarity of effects produced by A23187, and inophore which also increased 45Ca uptake. However, other mechanisms cannot be ruled out at the present time.
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PMID:Sialic acid: regulation of electrogenesis in cultured heart cells. 677 22

The aims of the present study were to demonstrate FcR activity of dental periapical granulomas and to correlate the activity with the degree of lymphoreticular cell infiltration. Cryostat sections of 46 out of 51 granulomas adsorbed sheep erythrocytes(E) sensitized with rabbit IgG antibodies (A) (EA). No adsorption occurred using erythrocytes sensitized with F(ab')2 fragments of IgG. IgG and Fc fragments of human of rabbit IgG inhibited the binding of EA, whereas F(ab')2 fragments, human IgA, IgM or albumin did not, indicating the presence of receptors for the Fc region of IgG. Periodate, neutral formaldehyde and phospholipase C abolished the FcR activity whereas neuraminidase had no effect. Comparison of sections binding EA and adjacent sections stained with haematoxylin and eosin showed that EA adhered to areas infiltrated with mononuclear cells. The degree of binding of EA coincided with the density of mononuclear cell infiltration. Point attachments between the tissue sections and the adsorbed EA could be demonstrated by scanning electron microscopy. Sections with no infiltrates did not bind EA.
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PMID:In situ characterization of cell infiltrates in human dental periapical granulomas. 1. Demonstration of receptors for the Fc region of IgG. 680 Dec 41

The composition, topological distribution and biological significance of phospholipids in the membrane of Newcastle disease virus (NDV) grown in embryonated chicken eggs were investigated. Phosphatidylethanolamine and sphingomyelin were the predominant phospholipids in NDV membrane. The location of phospholipids in the lipid bilayer of the membrane was studied by assessing their reactivities with highly purified phospholipase A2 (Agkistrodon halys blomhoffi) and phospholipase D (Streptomyces chromofuscus), and the biological role of membrane phospholipids was also investigated by using pure phospholipases A2, C (Bacillus cereus) and D. Choline-containing phospholipids were found predominantly in the outer layer of the membrane. The inner layer was composed mainly of aminoglycerophospholipids, though a fair amount of them also appeared to be located in the outer half of the bilayer. When intact virion was treated with phospholipase C, marked decreases in hemolytic activity and infectivity mediated by viral fusion (F) glycoprotein were observed, but hemagglutinating and neuraminidase activities did not change significantly. Apparently complete hydrolysis of phospholipids in the outer half of the lipid bilayer with phospholipase D caused about 22% decrease in the original hemolytic activity. On the other hand, when all phosphatidylcholine and aminoglycerophospholipids in the outer half of the viral membrane were hydrolyzed with purified phospholipase A2, no significant change in viral hemolytic activity or morphology was detected. No marked change of hemagglutinating and neuraminidase activities was detected on treatment of NDV with phospholipases A2 and D. The above results suggest that the integrity of fatty acid ester of glycerophospholipids in NDV membrane is not essential for the manifestation of viral activities, though polar groups of the phospholipids in the outer half of the membrane may be involved in the function of fusion (F) glycoprotein, but not in that of hemagglutinating and neuraminidase (HN) glycoprotein of NDV.
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PMID:Topological location and biological significance of phospholipids in the membrane of Newcastle disease virus. Hydrolysis of phospholipids in intact virion with pure phospholipases A2, C, and D. 713 Jan 58

The hemoglobin binding sites on the inner surface of the erythrocyte membrane were identified by measuring the fraction of hemoglobin released following selective proteolytic or lipolytic enzyme digestion. In addition, binding stoichiometry to and fractional hemoglobin release from inside-out vesicle preparations of human and rabbit membranes were compared since rabbit membranes differ significantly from human membranes only in that they lack glycophorin. Our results show that rabbit inside-out vesicles bind about 65% less human or rabbit hemoglobin under conditions of optimal and stoichiometric binding, despite being otherwise similar in composition. We suggest that this difference is either directly or indirectly due to the absence of glycophorin in rabbit membranes. Further supportive evidence includes demonstrating (a) that neuraminidase treatment of human membranes did not affect hemoglobin binding and (b) that reconstitution of isolated glycophorin into phospholipid vesicles increased the hemoglobin binding capacity in a manner proportional to the fraction of glycophorin molecules oriented with their cytoplasmic sides exposed to the exterior of the vesicle. Proteolysis of human inside-out vesicles either before or after addition of hemoglobin reduced the binding capacity by about 25%. This is consistent with the known proportion of total hemoglobin binding sites involving band 3 protein and the selective lability of the cytoplasmic aspect of band 3 protein to proteolysis. Phospholipid involvement in hemoglobin binding was determined using various phospholipase C preparations which differ in their reactivity profiles. Approximately 38% of the bound hemoglobin was released upon cleavage of phospholipid headgroups. These results suggest that the predominant sites of binding for hemoglobin on the inner surface of the red cell membrane are the two major integral membrane glycoproteins.
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PMID:Identification of the hemoglobin binding sites on the inner surface of the erythrocyte membrane. 717

Model systems simulating the cementum portion of teeth were used to characterize the attachment process by which certain species of oral Cytophaga initiate the colonization of the tooth root surface in vitro. The adsorption of these bacteria to spheroidal hydroxyapatite beads and mechanically powdered root material followed Langmuir isotherm kinetics. From such data, the number of binding sites per 20 mg of substrate and the affinity constants were evaluated for two strains of Cytophaga sp. Resting cells of the two strains tested adhered relatively tenaciously to hydroxyapatite beads in numbers similar to those observed with cells of Streptococcus sanguis. Attachment of bacteria to the substrates was partially inhibited by (i) coating the substrates with human serum or saliva, (ii) pretreating cell suspensions with proteinase K or phospholipase C or D, or (iii) exposing the cells to temperatures greater than 60 degrees C for 15 min. Treating resting cell suspensions with pronase, neuraminidase, phospholipase A2, or 0.1 M ethylenediaminetetraacetic acid had no effect on the attachment process.
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PMID:Attachment of oral Cytophaga species to hydroxyapatite-containing surfaces. 721 36

By using a suckling mouse assay, heat-stable enterotoxin (ST) was purified from the culture filtrate of Yersinia enterocolitica isolated from a diarrheal patient. The purification procedures involve ultrafiltration with an Amicon HIP-10 hollow fiber, ethanol fractionation, protamine sulfate treatment, diethylaminoethyl-Sephacel and hydroxylapatite column chromatographies, and Sephacryl S-200 superfine gel filtration. About 408-fold purification was achieved, with a yield of 12.0%. The minimal effective dose of purified ST was about 110 ng in the suckling mouse assay. The molecular weight of purified ST was 9,000 by Sephadex G-100 superfine gel filtration. The purified ST was stable to heating (100 degrees C for 20 min, 121 degrees C for 20 min) and did not lose its toxicity after treatment with protease, trypsin, lipase, phospholipase C, ribonuclease, deoxyribonuclease, beta-glucosidase, and neuraminidase. The purified ST was separated by isoelectric focusing into two active fractions, with pI's of 3.29 (ST-1) and 3.00 (ST-2), respectively. Antiserum from guinea pigs immunized with the purified ST neutralized the activity of both Y. enterocolitica ST and Escherichia coli ST.
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PMID:Partial purification and characterization of heat-stable enterotoxin produced by Yersinia enterocolitica. 721 60


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