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)

We labeled IgG with phospholipase C, using 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide. Enzymaticactivity of the resulting conjugate was inhibited when it was complexed with human IgG, but rabbit or goat IgG was not effective in suppressing the enzyme activity. Normal erythrocytes were used as substrate for the enzyme, enzymatic activity being assessed by measuring the release of hemoglobin. The substrates for phospholipase C are phospholipids, which are major components of the erythrocyte membranes. Hence, the phospholipids in the membranes are viewed as being "immobilized." Perhpas such immobilization of substrate may be a requisite to the inhibition phenomenon.
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PMID:Preparation of a phospholipase C-antihuman IgG conjugate, and inhibition of its enzymatic activity by human IgG. 30 45

We report here the inhibition of enzyme activity of phospholipase C-anti-human rabbit IgG conjugate complexed with human IgG. Phospholipase C activity was measured by assaying the release of hemoglobin from erythrocytes. The degree of inhibition varies depending on the relative amount of IgG utilized. A water soluble carbodiimide linking yields a conjugate which is inhibited by IgG, while conjugate prepared by glutaraldehyde is not. Immunodiagnostic assays requiring detection of low levels of antigen or antibody may be possible utilizing the phospholipase C-erythrocyte technique.
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PMID:Phospholipase C-labeled anti-human IgG: inhibition by human IgF. 32 66

Hemolysis induced by staphylococcal alpha-toxin, staphylococcal beta-toxin, streptolysin O, and streptolysin S was inhibited by zinc ions by virtue of inhibition of an early step in the events leading to lysis, presumably by preventing the lysins from attaching to the plasma membrane. In contrast, in hemolysis induced by Clostridium perfringens alpha-toxin and by perfringolysin O, a later step was inhibited by zinc. In hemolysis caused by saponin, lysolecithin, and Triton X-100, hemoglobin was precipitated by zinc ions as it was released from the erythrocyte. Inhibition by zinc was abolished by several amino acids of which L-histidine was the most effective.
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PMID:Inhibition of hemolysis by zinc and its reversal by L-histidine. 64 Jul 26

Platelet activating factor (PAF) stimulated aggregation and [32P]-phosphatidic acid (PA) production was compared in normal and diabetic human subjects in platelet rich plasma. The concentration of PAF for half maximal (50%) aggregation of normal and diabetic platelets was 50 nM and 8 nM, respectively. PAF stimulated [32P]-PA production (a metabolite of phospholipase C pathway) was also greater in the platelets from diabetic subjects. This [32P]-PA production was inhibited by the PAF receptor antagonists SRI-63441 and SRI-63675. When the levels of glycosylated hemoglobin (HbA1c) were compared with the PAF stimulated [32P]-PA production a significant relationship was observed. These studies have demonstrated for the first time that diabetic human platelets show hypersensitivity to PAF in both aggregation and [32P]-PA production compared to normal subjects. This may be a result of some modification in phospholipid turnover mechanism and is receptor mediated. Further, the relationship of the degree of aggregation and [32P]-PA production to the level of HbA1c suggest that the insulin deficiency may contribute to these effects.
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PMID:Hypersensitivity of diabetic human platelets to platelet activating factor. 132 54

Histamine produces a rapid and massive increase of the c-GMP level of guinea-pig lung tissue. The EC50 value for this in vitro response is found to be 27 microM and the c-GMP level is maximally 9-fold elevated by 100 microM histamine. The response is stereoselectively inhibited by the enantiomers of chlorpheniramine, indicating H1-receptor involvement. Preincubation of lung tissue with 200 microM NCDC, a phospholipase C inhibitor, reduces the histamine (100 microM) responses to 16 +/- 3% (N = 6) of the control c-GMP production. Inhibition of protein kinase C by 50 microM H-7 does not significantly attenuate the H1-receptor response, whereas omittance of extracellular Ca2+ results in almost complete inhibition of the c-GMP production. The histamine-induced c-GMP response is inhibited by hemoglobin, methylene blue and the antioxidants butylated hydroxytoluene and nordihydroguaretic acid, indicating the involvement of a nitric oxide-dependent activation of soluble guanylate cyclase. This suggestion is supported by the concentration-dependent inhibition of the c-GMP production by NG-monomethyl-L-arginine (NMA). At a concentration of 20 microM NMA the histamine (100 microM) response is inhibited to 34 +/- 8% (N = 6) of the control response. This inhibition is reversed to 127 +/- 20% (N = 6) by the exogenous addition of 1 mM L-arginine. These findings show that after an initial H1-receptor-mediated, phospholipase C-dependent, Ca(2+)-mobilization the enzymatic conversion of L-arginine to nitric oxide is stimulated. This nitric oxide production is finally responsible for the activation of soluble guanylate cyclase, leading to the production of c-GMP.
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PMID:Histamine H1-receptor-mediated cyclic GMP production in guinea-pig lung tissue is an L-arginine-dependent process. 165 Feb 6

Factor X-activating activity (FXAA) was determined by a chromogenic assay in normal and malignant breast tissue. FXAA was found in all tissue (n = 38) irrespective of pathology, and the activity of normal tissue was similar to that of tumours. FXAA correlated with tissue hemoglobin in normal breast (p less than 0.02) but not in tumours. FXAA was markedly reduced by aluminium hydroxide, barium citrate, anti-human factor VII, DFP, PMSF and phospholipase C, but was unaffected by iodoacetamide and mercuric chloride. It is concluded that FXAA is a serine protease with the properties of a tissue factor-factor VII complex. FXAA occurs in normal and malignant breast tissue, although the 'normal' activity may be an artefact of the homogenization process.
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PMID:Factor X-activating procoagulant in normal and malignant breast tissue. 228 55

To test the hypothesis that oxyhemoglobin causes contraction of vascular smooth muscle by production of inositol 1,4,5-trisphosphate which results in a release of intracellular calcium, smooth muscle cells were exposed to oxyhemoglobin and inositol trisphosphate was measured. Oxyhemoglobin, but not methemoglobin which has much less contractile action, stimulated inositol trisphosphate production. The time course was consistent with an early role for this compound in the contraction produced by hemoglobin. The increase in production of inositol trisphosphate was inhibited by pertussis toxin and also by neomycin, an inhibitor of phospholipase C, although the actions of the latter compound cannot be attributed only to an inhibition of the enzyme responsible for the production of inositol trisphosphate.
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PMID:Hemoglobin causes release of inositol trisphosphate from vascular smooth muscle. 239 5

Splenic erythroblasts obtained from BALB/c mice infected with the anemia strain of Friend virus were compared with "matured" cells and adult erythrocytes for their sensitivity to staphylococcal alpha-toxin. Matured cells were obtained by treating erythroblasts in culture with erythropoietin for 48 h. Sensitivity to staphylococcal alpha-toxin, measured both by release of 86Rb and by cell lysis, failed to demonstrate significant differences among the cell types. Since maturation of erythroblasts to matured cells or erythrocytes is associated with synthesis of band 3, hemoglobin, and spectrin and the loss of transferrin receptors, we conclude that none of these compounds serves as the specific receptor for staphylococcal alpha-toxin in BALB/c mice.
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PMID:Susceptibility to staphylococcal alpha-toxin of Friend virus-infected murine erythroblasts during differentiation. 398 78

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

There is general agreement that activation of the N-methyl-D-aspartate receptor is involved in thermal hyperalgesia. However, there is less agreement on the specific intracellular events subsequent to receptor activation and the involvement of other excitatory amino acid receptors in thermal hyperalgesia. In the present study, we found that the intrathecal administration of N-methyl-D-aspartate produced a dose- (1 fmol-1 pmol) and time-dependent thermal hyperalgesia. In contrast, over the dose range tested, intrathecal administration of either alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA; 10 fmol-100 pmol), 1,3-trans-1-aminocyclopentyl-1,3-dicarboxylate (10 fmol-100 pmol), quisqualate (10 pmol-5 nmol) or a 1:1 combination of AMPA and 1,3-trans-1-aminocyclopentyl-1,3-dicarboxylate (total dose 20 fmol-200 pmol) did not produce any evidence of thermal hyperalgesia; greater doses produced a caudally-directed biting and scratching behavior that precluded testing in the paradigm used. A fixed dose of 1,3-trans-1-aminocyclopentyl-1,3-dicarboxylate (100 pmol) did, however, potentiate the effects of N-methyl-D-aspartate (1-100 fmol). Thermal hyperalgesia produced by N-methyl-D-aspartate (1 pmol) was attenuated by intrathecal administration of the N-methyl-D-aspartate receptor-selective antagonist 2-amino-5-phosphonopentanoate (100 pmol), but not by the AMPA receptor-selective antagonist 6,7-dinitroquinoxaline-2,3-dione (1 nmol) or the metabotropic receptor antagonist 2-amino-3-phosphonoproprionate (10 nmol). In a second series of experiments, we examined the role of different signal transduction systems in acute N-methyl-D-aspartate-produced thermal hyperalgesia. N-Methyl-D-aspartate-produced thermal hyperalgesia (1 pmol) was attenuated by intrathecal hemoglobin (1-100 pmol) and dose-dependently by intrathecal N(G)-nitro-L-arginine methyl ester (10 pmol-l nmol), Methylene Blue (10 pmol-l nmol) and chelerythrine (1-100 pmol), suggesting that acute N-methyl-D-aspartate-mediated thermal hyperalgesia involves activation of nitric oxide synthase and protein kinase C. In contrast, N-methyl-D-aspartate-produced thermal hyperalgesia was unaffected by intrathecal administration of the phospholipase A2 inhibitor mepacrine (10 nmol) or the phospholipase C inhibitor neomycin (10 nmol). While prostaglandins and leukotrienes have been suggested to play a role in hyperalgesia, N-methyl-D-aspartate-produced thermal hyperalgesia (1 pmol) was unaffected by the non-selective eicosanoid inhibitor nordihydroguaiarate (1 nmol), the cyclo-oxygenase selective inhibitor indomethacin (10 nmol) or the lipoxygenase selective inhibitor baicalein (1 nmol). The results of the present study suggest that acute thermal hyperalgesia can be produced by activation of N-methyl-D-aspartate receptors. Activation of AMPA, metabotropic or co-activation of AMPA and metabotropic glutamate receptors, at the doses tested, did not produce an acute thermal hyperalgesia. The thermal hyperalgesia produced by N-methyl-D-aspartate is mediated by activation of nitric oxide synthase and protein kinase C, but not by phospholipase C, phospholipase A2, cyclo-oxygenase or lipoxygenase. Collectively, the results are consistent with a role for spinal N-methyl-D-aspartate receptors, nitric oxide and protein kinase C in thermal hyperalgesia.
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PMID:Acute thermal hyperalgesia in the rat is produced by activation of N-methyl-D-aspartate receptors and protein kinase C and production of nitric oxide. 905 88


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