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)

Some of the acute actions of insulin may be mediated by the intracellular generation of a chemical substance that modulates certain enzymes. Such a substance has been identified which is released from liver plasma membranes after exposure to insulin. This substance was purified on sequential ion exchange, reverse phase, and gel permeations columns. The purified substance modulated the activities of cAMP phosphodiesterase, adenylate cyclase, and pyruvate dehydrogenase. The activities that modulated each of these enzymes exhibited singular chromatographic behavior and sensitivity to a variety of chemical reagents. Each activity was also produced by treatment of membranes with a phosphatidylinositol-specific phospholipase C. These results suggested that each of the enzyme-modulating activities was due to a single complex carbohydrate substance which contained inositol, phosphate, glucosamine, and other monosaccharides. The actions of this substance on these three enzymes mimicked those of insulin, suggesting that the release of this enzyme modulator might play a role in mediating some of the actions of the hormone.
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PMID:Insulin generates an enzyme modulator from hepatic plasma membranes: regulation of adenosine 3',5'-monophosphate phosphodiesterase, pyruvate dehydrogenase, and adenylate cyclase. 302 92

BC3H-1 myocytes contain a phospholipid(s) which is labeled with [3H]inositol, [3H]glucosamine, and [3H]myristate [a phosphatidylinositol-glycan (PI-glycan)], and which is hydrolyzed by insulin induced activation of a specific phospholipase C. Similarly, epidermal growth factor and insulin-like growth factor-I provoke rapid increases in the hydrolysis of this PI-glycan, suggesting that derived signaling substances may be important in the action of agonists which activate tyrosine kinase type receptors.
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PMID:Epidermal growth factor and insulin-like growth factor I stimulate the hydrolysis of the insulin-sensitive phosphatidylinositol-glycan in BC3H-1 myocytes. 305 11

We have isolated a COOH-terminal tryptic peptide from the hydrophobic globular (5.6 S) form of Torpedo californica acetylcholinesterase that exhibits divergence in amino acid sequence from the catalytic subunit of the dimensionally asymmetric (17 S + 13 S) enzyme. The divergent peptide could be recovered from the glycophospholipid-modified 5.6 S enzyme only after treatment with phosphatidylinositol-specific phospholipase C. Upon reduction, carboxymethylation with [14C]iodoacetate, and trypsin digestion the resultant peptides were purified by gel filtration followed by high performance liquid chromatography. The high performance liquid chromatography profiles of 14C-labeled cysteine peptides from lipase-treated 5.6 S enzyme revealed unique radioactive peaks which had not been present in digests of the asymmetric form. These peaks all yielded identical amino acid sequences. The difference in chromatographic behavior of the individual peptides most likely reflects heterogeneity in post-translational processing. Gas-phase sequencing and composition analysis are consistent with the sequence: Leu-Leu-Asn-Ala-Thr-Ala-Cys. Composition includes 2-3 mol each of glucosamine and ethanolamine which is indicative of modification by glycophospholipid. Glucosamine is also present in an asparagine-linked oligosaccharide. The two forms of acetylcholinesterase diverge after the threonine residue within this peptide sequence; the hydrophobic form terminates with cysteine whereas the asymmetric form extends for 40 residues beyond the divergence. The locus of divergence and absence of any other amino acid sequence difference suggest that the molecular forms of acetylcholinesterase arise from a single gene by alternative mRNA processing.
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PMID:Divergence in primary structure between the molecular forms of acetylcholinesterase. 333 34

A glycophospholipid has been purified from rat liver membranes and shown to copurify with an insulin-sensitive glycophospholipid isolated from H35 hepatoma cells. The polar head group of this glycophospholipid is a phospho-oligosaccharide generated by treatment with phosphatidylinositol-specific phospholipase C from Staphylococcus aureus. It has been proposed that this phospho-oligosaccharide, which is also generated in response to insulin, may play a role in insulin action. Incubation of the catalytic subunit of cyclic AMP-dependent protein kinase with this phospho-oligosaccharide inhibited the activity of the kinase to phosphorylate histone IIA, a purified preparation of phospholipid methyltransferase and kemptide, a phosphate-accepting peptide. Inhibition of kinase activity was dose-dependent and 50% inhibition of histone phosphorylation was demonstrated with a concentration of phospho-oligosaccharide of around 2 microM. This effect was demonstrated in the presence of ATP at concentrations up to 1 mM, indicating that the phospho-oligosaccharide acts at physiological concentrations of ATP and that it does not compete with this nucleotide for the same binding site in the kinase. Inhibition by the phospho-oligosaccharide of kinase activity could be reversed by dilution or dialysis and was not reproduced by up to 50 microM myo-inositol, glucosamine, galactose, myo-inositol 1-phosphate, glucosamine 1-phosphate, galactose 1-phosphate or phosphorylcholine. The inhibitory activity was resistant to mild acid treatment but was labile to treatment with alkali, exposure to nitrous acid or incubation with sodium periodate. The phospho-oligosaccharide had no effect on the phosphorylation of lysine-rich histone by rat brain protein kinase C and on the binding of cyclic AMP to a cyclic AMP-dependent protein kinase. In conclusion, the data in this study suggested that a phospho-oligosaccharide generated from an insulin-sensitive glycophospholipid may play a role in insulin action by modulating cyclic AMP-dependent protein kinase activity.
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PMID:Inhibition of cyclic AMP-dependent protein kinase by the polar head group of an insulin-sensitive glycophospholipid. 333 45

Trypanosoma brucei variant surface glycoproteins are apparently synthesized with a hydrophobic carboxyl-terminal peptide that is cleaved and replaced by a complex glycosylphosphatidylinositol membrane anchor within 1 min of the completion of polypeptide synthesis. The rapidity of this carboxyl-terminal modification suggests the existence of a prefabricated core glycolipid that would be transferred en bloc to the variant surface glycoprotein polypeptide. We report the purification and chemical characterization of a glycolipid from T. brucei that has properties consistent with a role as a variant surface glycoprotein glycolipid donor. This candidate glycolipid precursor has been defined by thin-layer chromatography of extracts of trypanosomes metabolically labeled with radioactive myristic acid, ethanolamine, glucosamine, mannose, and phosphate and by enzymatic, chemical, and gas chromatographic-mass spectrometric analysis. Mild alkali released 100% of the myristic acid, and reaction with phospholipase A2 released 50%. Nitrous acid deamination generated dimyristylphosphatidylinositol, and periodate oxidation released phosphatidic acid. Treatment of purified glycolipid with phosphatidylinositol-specific phospholipase C released dimyristylglycerol and a water-soluble glycan that was sized on Bio-Gel P-4 columns. The candidate precursor contained mannose, myristic acid, phosphate, and ethanolamine with an unsubstituted amino group, but not galactose.
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PMID:Candidate glycophospholipid precursor for the glycosylphosphatidylinositol membrane anchor of Trypanosoma brucei variant surface glycoproteins. 333

The biosynthesis and post-translational modification of placental alkaline phosphatase were studied in human choriocarcinoma cells, JEG-3. Pulse-chase experiments with [35S]methionine demonstrated that placental alkaline phosphatase was synthesized as a major precursor form with Mr 63,000, which was then converted to a mature form with Mr 66,000, by processing of its N-linked oligosaccharides from the high-mannose type to the complex type. In addition, the two forms of the protein were found to be modified by a glycophospholipid, components of which were characterized by metabolic incorporation into placental alkaline phosphatase of 3H-labeled compounds such as myo-inositol, palmitic acid, stearic acid, mannose, glucosamine, and ethanolamine. When placental alkaline phosphatase labeled with these compounds was treated with phosphatidylinositol-specific phospholipase C or papain, the phospholipase C removed only the 3H-labeled fatty acids, whereas papain, that is known to cleave the C-terminal region, released all the radioactive glycolipid components including [3H]ethanolamine. More detailed analysis with shorter pulse-chase experiments demonstrated that placental alkaline phosphatase was primarily synthesized as a form with Mr 64,500 which was not yet labeled with [3H]palmitic acid. This form was converted by papain digestion to the above-mentioned major precursor with Mr 63,000. Taken together, these results suggest that placental alkaline phosphatase is initially synthesized as the precursor with Mr 64,500, which is immediately converted to the intermediate form with Mr 63,000 by simultaneously occurring proteolysis of the C terminus and replacement by the glycophospholipid, and finally to the mature form with Mr 66,000 by terminal glycosylation of its N-linked oligosaccharides. The glycophospholipid thus attached is considered to function as the membrane-anchoring domain of placental alkaline phosphatase.
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PMID:Biosynthesis of placental alkaline phosphatase and its post-translational modification by glycophospholipid for membrane-anchoring. 334 38

PC12 pheochromocytoma cells and cultures of early postnatal rat cerebellum were labeled with [3H]glucosamine, [3H]fucose, [3H]leucine, [3H]ethanolamine, or sodium [35S]sulfate and treated with a phosphatidylinositol-specific phospholipase C. Enzyme treatment of [3H]glucosamine- or [3H]fucose-labeled PC12 cells led to a 15-fold increase in released glycoproteins. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, most of the released material migrated as a broad band with an apparent molecular size of 32,000 daltons (Da), which was specifically immunoprecipitated by a monoclonal antibody to the Thy-1 glycoprotein. A second glycoprotein, with an apparent molecular size of 158,000 Da, was also released. After treatment with endo-beta-galactosidase, 40-45% of the [3H]glucosamine or [3H]fucose radioactivity in the phospholipase-released glycoproteins was converted to products of disaccharide size, and the molecular size of the 158-kDa glycoprotein decreased to 145 kDa, demonstrating that it contains fucosylated poly-(N-acetyllactosaminyl) oligosaccharides. The phospholipase also released labeled Thy-1 and the 158-kDa glycoprotein from PC12 cells cultured in the presence of [3H]ethanolamine, which specifically labels this component of the phosphatidylinositol membrane-anchoring sequence, while in the lipid-free protein residue of cells not treated with phospholipase, Thy-1 and a doublet at 46/48 kDa were the only labeled proteins. At least eight early postnatal rat brain glycoproteins also appear to be anchored to the membrane by phosphatidylinositol. Sulfated glycoproteins of 155, 132/134, 61, and 21 kDa are the predominant species released by phospholipase, which does not affect a major 44-kDa protein seen in [3H]ethanolamine-labeled brain cultures. The 44-48- and 155/158-kDa proteins may be common to both PC12 cells and brain.
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PMID:Phosphatidylinositol-anchored glycoproteins of PC12 pheochromocytoma cells and brain. 339 Apr 45

Acetylcholinesterases (AcChoEases; EC 3.1.1.7) from bovine (Ebo) and human (Ehu) erythrocytes were purified to apparent homogeneity by affinity chromatography. The hydrophobic portion of the glycolipid membrane anchor of each enzyme was radiolabeled with the photoactivated reagent 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine. Several cleavage procedures demonstrated that this radiolabel was highly selective for the fatty acid portion of the anchor in both enzymes. The labeled enzymes were digested with phosphatidylinositol (PtdIns)-specific phospholipase C (EC 3.1.4.10), and label release was assessed by polyacrylamide gel electrophoresis. About 85% of the radiolabel was cleaved from Ebo AcChoEase, whereas only 5% was released from Ehu AcChoEase. This finding agrees with a report that Ebo AcChoEase was quantitatively released from intact erythrocytes by PtdIns-specific phospholipase C but Ehu AcChoEase was not [Low, M. G. & Finean, J. B. (1977) FEBS Lett. 82, 143-146]. The two AcChoEases contained comparable amounts of the anchor components ethanolamine, glucosamine, and myo-inositol, but qualitative and quantitative differences were found in the fatty acids. Thin-layer chromatography of radiolabeled fragments generated from Ebo and Ehu AcChoEases by nitrous acid deamination revealed a major difference in the membrane anchors of the two enzymes. The fragment released from Ebo AcChoEase by this procedure comigrated with PtdIns, whereas the corresponding fragment from Ehu AcChoEase had a mobility much greater than that of PtdIns even though it contained myo-inositol and fatty acids. These studies show that 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine is useful for analysis of lipid-containing compounds and indicate that, whereas Ebo AcChoEase contains PtdIns in its glycolipid anchor, Ehu AcChoEase has a different anchor structure, which is resistant to PtdIns-specific phospholipase C. This observation suggests the existence of a class of glycolipid-anchored membrane proteins resistant to this phospholipase.
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PMID:Differences in the glycolipid membrane anchors of bovine and human erythrocyte acetylcholinesterases. 347 67

The major cell surface glycoconjugate of Leishmania major, a putative parasite receptor for macrophages, is a lipophosphoglycan containing 81.6% (wt/wt) carbohydrate, 17.0% (wt/wt) phosphate, and 1.4% (wt/wt) lipid. It has been purified to homogeneity by hydrophobic chromatography and consists of a polydisperse family of molecules with Mr 5000-40,000. It contains galactose, mannose, glucose, arabinose, glucosamine, and inositol in the molar ratio of 51:21:5:6:1:1. The lipophosphoglycan has a complex structure, consisting mainly of tri- and tetrasaccharide units linked by phosphodiester bonds, which are cleaved by HF hydrolysis. The phosphate groups are located on the 6-hydroxyl of both galactose and mannose residues. The lipophosphoglycan is anchored to the parasite surface by a 1-O-alkyl-sn-glycero-3-phosphoinositol moiety. This conclusion is supported by analysis of the products of nitrous acid deamination, HF hydrolysis, and Staphylococcus aureus phosphatidylinositol specific-phospholipase C treatment. The 24:0 and 26:0 alkyl chains accounted for 93% of the ether-linked fatty acids in the lipid anchor. The results are also consistent with a glycosidic linkage between the inositol and a non-N-acetylated glucosamine residue. The lipophosphoglycan membrane anchor shares limited structural homology with the glycosylphosphatidylinositol anchors of several eukaryotic proteins, indicating that this type of membrane anchor is not limited to proteins. Vaccination of mice with the purified L. major lipophosphoglycan in liposomes induced resistance against cutaneous leishmaniasis.
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PMID:Lipophosphoglycan of Leishmania major that vaccinates against cutaneous leishmaniasis contains an alkylglycerophosphoinositol lipid anchor. 348 May 20

We recently described the insulin-dependent release of a carbohydrate substance from plasma membranes which regulated certain intracellular enzymes (Saltiel, A. R., and Cuatrecasas, P. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 5793-5797). This enzyme-modulating substance appeared to arise from the phosphodiesterase hydrolysis of a novel inositol-containing glycolipid. This is supported by observations that insulin stimulated the rapid generation of [3H]myristate-labeled diacylglycerol in cultured BC3Hl myocytes. Myristoyl diacylglycerol production in these cells was unaffected by epinephrine, although arachidonate-labeled diacylglycerol was rapidly produced in response to stimulation by this alpha-1 adrenergic agent. The production of distinct species of diacylglycerol was apparently due to hormonally specific hydrolysis of different precursors. A novel glycolipid was identified on silica TLC or high pressure liquid chromatography which served as a substrate for the insulin-stimulated phosphodiesterase reaction. This glycolipid was metabolically labeled with radioactive inositol, glucosamine, and myristic acid, suggesting a phosphatidylinositol (PI)-glycan structure. Treatment of this glycolipid with a PI-specific phospholipase C resulted in the generation of two products: an inositol phosphate-glycan which modulated the activity of the low Km cAMP phosphodiesterase and myristoyl diacylglycerol. Insulin caused the rapid hydrolysis of the PI-glycan, which was then apparently resynthesized. These data further suggest that insulin stimulates the activity of a phospholipase C which selectively hydrolyzes a novel PI-glycan, releasing a carbohydrate enzyme modulator as well as a unique species of diacylglycerol.
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PMID:Insulin-stimulated diacylglycerol production results from the hydrolysis of a novel phosphatidylinositol glycan. 354 98


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