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)

A new type of globular particle, the 'insoluble yolk globule', was isolated from the egg yolk of three avian species (hen, duck, and emu) by centrifugation or gel-filtration chromatography. These globules are stable in NaCl and urea solutions at concentrations that dissolve or disrupt other constituents of yolk, The isolated globules are about 1% of the dry yolk of hen's and duck's eggs but about 8% emu's-egg yolk. Most of these globules are less than 2 micrometer in diameter. Electron micrographs of sections show a preponderance of globules in the range 0.125-0.25 micrometer, each with a thick shell surrounding a feature-less anterior. Globules with the same appearance were seen in sections of unfractionated yolk. Two kinds of larger particles were also observed: (i) particles with a distinct outer membrane and a vesiculated interior; (ii) featureless spheres, possibly of lipid. The insoluble yolk globules comprise protein (8-11% by dry wt.), phospholipid (31-35% total lipid), triacylglycerols (49-53%), cholesterol (8%) and cholesteryl esters (2-3%); the variations being among species. The phospholipid is accessible to phospholipase C. The isolated protein is heterogeneous and resembles the apoprotein from the yolk low-density lipoprotein.
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PMID:Lipid-protein globules of avian egg yolk. Isolation and properties of globules stable in concentrated sodium chloride solution. 56 17

Amastigotes of Leishmania major were isolated from infected mice and radiolabeled for 2 h with [3H]galactose. An acidic [3H]glycoconjugate was extracted from a dilipidated residue fraction with the solvent water/ethanol/diethylether/pyridine/NH4OH (15:15:5:1:0.017). The radioactivity labeled glycoconjugate was found to possess the following characteristics that were similar to the lipophosphoglycan extractable from promastigotes: (i) migrated as a broad band upon electrophoresis on SDS polyacrylamide gels; (ii) deaminated with nitrous acid; and (iii) hydrolyzed with phosphatidylinositol-specific phospholipase C. Furthermore, analysis of the aqueous soluble material released by the latter enzyme revealed a negatively-charged [3H]polysaccharide intermediate in size compared to the analogous portions of LPG isolated from non-infective and metacyclic promastigotes. Most importantly, the [3H]polysaccharide was found to contain phosphate and was susceptible to mild acid hydrolysis, establishing that the intact molecule is a lipophosphoglycan. A structural difference, however, was found in the major, mild acid-generated fragment of the amastigote phosphoglycan, which was larger in size and not as anionic as the analogous fragment from the promastigote phosphoglycans. These results indicate that the amastigotes do express a lipophosphoglycan, but that it is structurally distinct from its promastigote counterparts.
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PMID:Expression of a stage-specific lipophosphoglycan in Leishmania major amastigotes. 164 60

Fragments of the lipophosphoglycan of Leishmania donovani were generated by phospholipase C digestion and mild acid hydrolysis. The fragments were purified and examined for inhibitory activity on protein kinase C isolated from rat brains. On a molar basis, the 1-O-alkylglycerol portion of LPG exhibited the most inhibitory activity, whereas the carbohydrate domain was not as effective. In addition, several glycolipid antigens from L. major, which contain short carbohydrate chains attached to phosphatidylinositol, were also efficient inhibitors of the enzyme. These results are consistent with the hypothesis that protein kinase C may be a key target for the parasites to overcome within host macrophages.
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PMID:Inhibitory effects on protein kinase C activity by lipophosphoglycan fragments and glycosylphosphatidylinositol antigens of the protozoan parasite Leishmania. 252 91

Low density lipoprotein (LDL) modified by incubation with phospholipase C (PLC-LDL) aggregates in solution and is rapidly taken up and degraded by human and mouse macrophages, producing foam cells in vitro. Human, mouse, and rabbit macrophages degraded 125I-labeled PLC-LDL (125I-PLC-LDL) more rapidly than native 125I-labeled LDL (125I-LDL), while nonphagocytic cells such as human fibroblasts and bovine aortic endothelial cells degraded 125I-PLC-LDL more slowly than 125I-LDL. This suggested the mechanism for internalization of PLC-LDL was phagocytosis. When examined by electron microscopy, mouse peritoneal macrophages appeared to be phagocytosing PLC-LDL. The uptake and degradation of 125I-PLC-LDL by human macrophages was inhibited greater than 80% by the monoclonal antibody C7 (IgG2b) produced by hybridoma C7, which blocks the ligand binding domain of the LDL receptor. Similarly, methylation of 125I-LDL (125I-MeLDL) prior to treatment with phospholipase C decreased its subsequent uptake and degradation by human macrophages by greater than 90%. The uptake and degradation of phospholipase C-modified 125I-MeLDL by macrophages could be restored by incubation of the methylated lipoprotein with apoprotein E, a ligand recognized by the LDL receptor. These results indicate that macrophages internalize PLC-LDL by LDL receptor-dependent phagocytosis.
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PMID:Phagocytosis of aggregated lipoprotein by macrophages: low density lipoprotein receptor-dependent foam-cell formation. 270 43

We have reported the existence of a novel form of coagulation factor VII - probably a factor VII-phospholipid complex - in plasma from pregnant women and men at risk for cardiovascular disease. We report here further observations on the presence and characteristics of this complex. Some apparently healthy individuals who, on testing by standard methods, have normal levels of factor VII activity achieve such levels by means of a phospholipase C-sensitive modification of (some of) their factor VII molecules. Their residual factor VII activity after phospholipase C treatment of plasma may be as low as 10-20 U/ml. Antiserum to the protein component of thromboplastin (apoprotein III) had no effect on the factor VII activity, whereas antiserum to factor VII effectively blocked both the total factor VII activity and the residual activity of factor VII after treatment of plasma with phospholipase C. These factor VII complexes precipitate with the VLDL/LDL fraction in lipoprotein precipitations.
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PMID:A new form of coagulation factor VII in plasma. 309 Jun 80

The hypercoagulable state in pregnancy is partly caused by the increased activity of factor VII in plasma. We demonstrate here that this activity is reduced to levels similar to those in plasma from non-pregnant women by highly purified phospholipase C from Bacillus cereus, i.e. the activity increase is due to a circulating complex of factor VII and a phospholipase C-sensitive compound. Phospholipase C had no effect on the levels of factor II and X in blood from pregnant women. This novel form of activated factor VII is not inhibited by an antiserum to the protein component of thromboplastin (apoprotein III). By gel filtration of plasma from pregnant women on Sephadex G-100 the phospholipase C-sensitive complex was partly separated from non-phospholipase sensitive factor VII also present in the same plasma.
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PMID:The coagulation factor VII in pregnancy. 660 66

Treatment of cholesterol-loaded mouse peritoneal macrophages with exogenous phospholipase C results in a specific and dose-dependent inhibition of apoE secretion. The inhibition of apoE secretion is secondary to the rapid and specific inhibition of its synthesis. The profound changes in rates of apoE synthesis are not accompanied by changes in the levels of apoE mRNA, an observation strongly suggestive of translational regulation of expression. The changes in apoE expression coincide with, or are preceded by a three-fold increase in membrane-bound protein kinase C activity, pointing out the potential importance of this signal transduction pathway in regulating apoE expression at a posttranscriptional locus.
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PMID:Exogenous phospholipase C specifically inhibits apoE expression in mouse peritoneal macrophages. 834 68

Following a 1 h incubation of human platelets with low-density lipoprotein (LDL) labelled in the apoprotein fraction (125I-apoB) or in phospholipid fractions [14C-labelled phosphatidylcholine (PC), phosphatidylethanolamine (PE) or sphingomyelin (SM)], the percentage of total 14C associated with the cells was about 3-fold higher than the percentage of 125I. Differences in temperature sensitivity also indicated differential interactions of phospholipids and apoprotein with platelets. In order to assess the amount of [14C]phospholipid transferred from LDL or high-density lipoprotein (HDL) to the cells, the quantity of bound lipoproteins was estimated by adding an excess of unlabelled lipoprotein, or by selectively degrading LDL- and HDL-associated [14C]PC and [14C]PE with phospholipase C. Incubation of platelets with LDL or HDL containing pyrenedecanoic acid-labelled PC or SM (py-PC, py-SM) increased pyrene monomer fluorescence, indicating incorporation of the phospholipids into platelets. With HDl as donor, incorporation of py-SM was greater than uptake of py-PC. Pretreating platelets with elastase dose-dependently inhibited uptake of py-SM and py-PC. Treatment of cells with phospholipase C indicated that the uptake of [14C]PC by platelets, and not the binding of lipoproteins to the cells, was partially inhibited by elastase. In conclusion, LDL and HDL rapidly deliver SM, PC and PE to platelets. Incorporation of LDL-derived phospholipids into platelets is unlikely to be mediated by endocytosis of lipoprotein particles. The uptake of the two choline-containing phospholipids appears to require the presence of specialized platelet membrane protein(s).
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PMID:Transfer of phosphatidylcholine, phosphatidylethanolamine and sphingomyelin from low- and high-density lipoprotein to human platelets. 864 58

The N-terminal domain of human apolipoprotein E (apoE-NT) harbors residues critical for interaction with members of the low-density lipoprotein receptor (LDLR) family. Whereas lipid free apoE-NT adopts a stable four-helix bundle conformation, a lipid binding induced conformational adaptation is required for manifestation of LDLR binding ability. To investigate the structural basis for this conformational change, the short helix connecting helix 1 and 2 in the four-helix bundle was replaced by the sequence NPNG, introducing a beta-turn. Recombinant helix-to-turn (HT) variant apoE3-NT was produced in Escherichia coli, isolated and characterized. Stability studies revealed a denaturation transition midpoint of 1.9 m guanidine hydrochloride for HT apoE3-NT vs. 2.5 M for wild-type apoE3-NT. Wild-type and HT apoE3-NT form dimers in solution via an intermolecular disulfide bond. Native PAGE showed that reconstituted high-density lipoprotein prepared with HT apoE3-NT have a diameter in the range of 9 nm and possess binding activity for the LDLR on cultured human skin fibroblasts. In phospholipid vesicle solubilization assays, HT apoE3-NT was more effective than wild-type apoE3-NT at inducing a time dependent decrease in dimyristoylphosphatidylglycerol vesicle light scattering intensity. In lipoprotein binding assays, HT apoE3-NT protected human low-density lipoprotein from phospholipase C induced aggregation to a greater extent that wild-type apoE3-NT. The results indicate that a mutation at one end of the apoE3-NT four-helix bundle markedly enhances the lipid binding activity of this protein. In the context of lipoprotein associated full-length apoE, increased lipid binding affinity of the N-terminal domain may alter the balance between receptor-active and -inactive conformational states.
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PMID:Replacement of helix 1' enhances the lipid binding activity of apoE3 N-terminal domain. 1642 Apr 79

Oxidation of dietary cholesterol during food storage and processing, and/or that of endogenous cholesterol in the presence of increased steady-state levels of reactive oxygen species, leads to the production of derivatives, termed oxysterols. Among the biochemical effects exerted by an oxysterol mixture, it has recently been observed that marked up-regulation of CD36 scavenger receptor on macrophage cells plays a primary role in foam cell formation. This article reports evidence of a significant co-localization of CD36 receptor with cells of the macrophage lineage, i.e. CD68 positive cells, LDL apoprotein B100 and lipids in human advanced atherosclerotic lesions. In addition, it provides a comprehensive analysis of the molecular signaling operated by a nutritionally relevant mixture of oxysterols in overexpressing CD36 receptor in cells of the macrophage lineage. The involvement of a G protein, Src, phospholipase C cascade and peroxisome proliferator-activated receptor gamma in oxysterol-mediated signaling was demonstrated by using selective inhibitors, while the central role of the downstream protein kinase Cdelta and extracellular signal-regulated kinase pathways in oxysterol-induced enhancement of CD36 was conclusively proved by means of small interfering RNA (siRNA) technology.
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PMID:Molecular signaling operated by a diet-compatible mixture of oxysterols in up-regulating CD36 receptor in CD68 positive cells. 2033 25


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