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)

Thy-1 is a developmentally regulated cell surface glycoprotein in nervous tissue. An inositol-containing glycolipid structure is covalently attached to its carboxyl terminus, which anchors the protein to the cell membrane. In the present paper we report the characterization of a water-soluble form of Thy-1, purified from human cerebrospinal fluid (CSF). In contrast to the membrane-bound form of Thy-1 (M-Thy-1) isolated from human brain cerebral cortex, CSF-Thy-1 behaved like a completely hydrophilic glycoprotein, as analyzed by charge-shift electrophoresis in the presence of detergents and by liposome incorporation experiments. CSF-Thy-1 displayed a slightly higher apparent molecular weight in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than M-Thy-1. Digestions with endoglycosidases demonstrated that this difference in size was correlated to different processing of the three N-linked oligosaccharides, and the mobilities of the deglycosylated molecules were indistinguishable in sodium dodecyl sulfate gels. A Pronase-resistant carboxyl-terminal fragment was isolated from the CSF-Thy-1 after trypsin digestion and compared with the corresponding structure of M-Thy-1, obtained by treatment either with bacterial phosphatidylinositol-specific phospholipase C or with human serum (as a source of phosphatidylinositol-specific phospholipase D). The major fragment from CSF-Thy-1 behaved identically, with respect to size and charge, to the carboxyl-terminal fragment from M-Thy-1 solubilized by phospholipase D. These findings suggest an in vivo release of phosphatidylinositol-anchored Thy-1 glycoprotein from brain cells by the action of an endogenous phospholipase D.
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PMID:Characterization of a hydrophilic form of Thy-1 purified from human cerebrospinal fluid. 290 Aug 38

Investigations on the turnover of the membrane-form variant surface glycoprotein (mfVSG) of Trypanosoma brucei during cultivation in vitro of the monomorphic variant clones MIT at 1.2 and MIT at 1.4 showed that bloodstream forms slowly released the surface coat into the medium (time required to decline to half the initial amount, t50% = 32 +/- 3 h). VSG appeared in the medium in its soluble form (sVSG) which lacked the dimyristoylglycerol membrane anchor as judged by electrophoretic mobility and exposure of the cross-reacting determinant. The total VSG in the culture was very stable with a t50% = 189 +/- 24 h, compared to the other cellular proteins with a t50% approximately 28 h. Coat release during differentiation of bloodstream forms to procyclic cells could be distinguished from this turnover both by its more rapid kinetics (t50% = 13 +/- 1 h) and by the appearance in the medium of a predominant proteolytic fragment in addition to sVSG. Coat release during the transition to procyclic forms was not inhibited by the lysosomotropic agents ammonium chloride or chloroquine, by the proton ionophore monensin, or by the protease inhibitor tosyl-L-lysine chloromethyl ketone. The experiments demonstrate that coat release during differentiation is a specific cellular event distinct from simple turnover. The possibility is discussed that VSG release under both conditions occurs by endocytosis of mfVSG, degradation by a phospholipase C or a protease or both in a non-acidic intracellular compartment and recycling to the surface by exocytosis.
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PMID:Release of the variant surface glycoprotein during differentiation of bloodstream to procyclic forms of Trypanosoma brucei. 291 Dec 81

A monoclonal antibody MEM-43 was prepared, which recognizes an antigen expressed on all peripheral blood leucocytes, on erythrocytes and several cell lines, but is absent from U937, Nalm-6, Daudi and Raji cell lines. The antigen isolated by immunoaffinity chromatography from several cell lines is an 18,000-25,000 mol. wt glycoprotein. An apparently identical antigen isolated from erythrocytes binds to several lectins and has a 14,000 mol. wt polypeptide backbone, modified by an endoglycosidase F-sensitive carbohydrate moiety. The epitope recognized is reduction-sensitive. The sequence of N-terminal 17 amino acid residues was determined; five out of six N-terminal amino acids are identical to those found at the N-terminus of the mouse lymphocyte surface antigen Ly-6C. The antigen is completely released from the cell surface after treatment with phosphatidylinositol-specific phospholipase C.
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PMID:Characterization of a broadly expressed human leucocyte surface antigen MEM-43 anchored in membrane through phosphatidylinositol. 291 59

P30, the major surface antigen of the parasitic protozoan Toxoplasma gondii, can be specifically labeled with [3H]palmitic acid and with myo-[2-3H]inositol. The fatty acid label can be released by treatment of P30 with phosphatidylinositol-specific phospholipase C (PI-PLC). Such treatment exposes an immunological "cross-reacting determinant" first described on Trypanosoma brucei variant surface glycoprotein. PI-PLC cleavage of intact parasites metabolically labeled with [35S]methionine results in the release of intact P30 polypeptide in a form which migrates faster in polyacrylamide gel electrophoresis. These results argue that P30 is anchored by a glycolipid. Results from thin layer chromatography analysis of purified [3H] palmitate-labeled P30 treated with PI-PLC, together with susceptibility to mild alkali hydrolysis and to cleavage with phospholipase A2, suggest that the glycolipid anchor of T. gondii P30 includes a 1,2-diacylglycerol moiety.
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PMID:The major surface antigen, P30, of Toxoplasma gondii is anchored by a glycolipid. 292 21

Renal dipeptidase (EC 3.4.13.11) was solubilized from pig kidney microvillar membranes with bacterial phosphatidylinositol-specific phospholipase C and then purified by affinity chromatography on cilastatin-Sepharose. The enzyme was apparently homogeneous on SDS/polyacrylamide-gel electrophoresis with an Mr of 47,000. Immunohistochemical analysis of the distribution of the dipeptidase showed it to be concentrated in the brush-border region of the proximal tubules in close association with endopeptidase-24.11) (EC 3.4.24.11). The purified dipeptidase was shown to contain 1 mol of inositol/mol and to possess the cross-reacting determinant characteristic of the glycosyl-phosphatidylinositol membrane-anchoring domain. The glycoprotein nature of renal dipeptidase was confirmed by chemical and enzymic deglycosylation. These results establish renal dipeptidase as a glycosyl-phosphatidylinositol-anchored ectoenzyme of the microvillar membrane.
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PMID:Ectoenzymes of the kidney microvillar membrane. Affinity purification, characterization and localization of the phospholipase C-solubilized form of renal dipeptidase. 293 Apr 55

We have analysed the structures of the Trypanosoma (Nannomonas) congolense and T. equiperdum variant surface glycoprotein (VSG) membrane anchors. Myristic acid uptake, phospholipase treatment, and nitrous acid deamination showed that, for each species, the anchor is glycosyl-sn-1,2-dimyristylphosphatidylinositol, as has been previously described for T. brucei. Osmotic lysis of these trypanosomes resulted in the release of soluble VSG, lacking fatty acid. In both species and in T. evansi, an endogenous phospholipase C, which cleaved diacylglycerol from membrane form VSG, was identified.
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PMID:Glycosyl-sn-1,2-dimyristylphosphatidylinositol is the membrane anchor for Trypanosoma equiperdum and T. (Nannomonas) congolense variant surface glycoproteins. 295 88

Alkaline phosphatase in a wide range of tissues has been shown to be anchored in the membrane by a specific interaction with the polar head group of phosphatidylinositol. It has previously been suggested that the production of low Mr alkaline phosphatase during the commonly used butanol extraction procedure may result from the activation of an endogenous phosphoinositide-specific phospholipase C which removes the 1,2-diacylglycerol responsible for membrane anchoring. This conversion process was investigated in greater detail with human placenta used as the source of alkaline phosphatase. Mr and hydrophobicity of the alkaline phosphatase were determined by gel filtration on TSK-250 and partitioning in Triton X-114, respectively. Alkaline phosphatase extracted from human placental particulate fraction with butanol at pH 5.4 or released by incubation with Staphylococcus aureus phosphatidylinositol-specific phospholipase C produced a form of alkaline phosphatase of Mr approx. 170,000 and relatively low hydrophobicity. By contrast, the butanol extract prepared at pH 8.3 was an aggregated form of Mr approx. 600,000 and was relatively hydrophobic. The effect of a variety of inhibitors and activators on the amount of low Mr alkaline phosphatase produced during butanol extraction revealed that it was a Ca2+- and thiol-dependent process. Proteinase inhibitors had no effect. [3H]Phosphatidylinositol hydrolysis by the particulate fraction, unlike low Mr alkaline phosphatase production, was relatively sensitive to heat inactivation, indicating that the phosphoinositide-specific phospholipases C from cytosol and lysosomes were unlikely to be responsible for conversion. A butanol-stimulated activity which removed the [3H]myristic acid from the variant surface glycoprotein ( [3H]mfVSG) of Trypanosoma brucei was detectable in the human placental particulate fraction. Since this activity was acid active, Ca2+- and thiol-dependent and relatively heat stable, it may be the same as that responsible for production of low Mr alkaline phosphatase. The only 3H-labelled product identified was phosphatidic acid, suggesting that the [3H]mfVSG-cleaving activity is a phospholipase D. These data strongly support the proposal that production of low Mr alkaline phosphatase during butanol extraction is an autolytic process occurring as the result of an endogenous phospholipase. However, they also suggest that the lysosomal and cytosolic phosphoinositide-specific phospholipases C that have previously been described in many mammalian tissues are not responsible for this process.
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PMID:Conversion of human placental alkaline phosphatase from a high Mr form to a low Mr form during butanol extraction. An investigation of the role of endogenous phosphoinositide-specific phospholipases. 302 77

A major glycoprotein of rat hepatoma plasma membranes was selectively released as a soluble form by incubating the membrane with phosphatidylinositol-specific phospholipase C. The soluble form corresponding to the glycoprotein was also prepared by butan-1-ol extraction of microsomal membranes at pH 5.5, whereas extraction at pH 8.5 yielded an electrophoretically different form with a hydrophobic nature. The soluble glycoprotein extracted at pH 5.5 was purified by sequential chromatography on concanavalin A-Sepharose, Sephacryl S-300 and anti-(alkaline phosphatase) IgG-Sepharose, the last step being used to remove a contaminating alkaline phosphatase. The glycoprotein thus purified was a single protein with Mr 130,000 in SDS/polyacrylamide-gel electrophoresis, although it behaved as a dimer in gel filtration on Sephacryl S-300. The glycoprotein was analysed for amino acid and carbohydrate composition. The composition of the carbohydrate moiety, which amounted to 64% by weight, suggested that the glycoprotein contained much larger numbers of N-linked oligosaccharide chains than those with O-linkage. It was confirmed that the purified glycoprotein was immunologically identical not only with that released by the phospholipase C but also with the hydrophobic form extracted with butan-1-ol at pH 8.5. The results indicate that the glycoprotein of rat hepatoma plasma membranes, which has an unusually high content of carbohydrate, is another membrane protein released by phosphatidylinositol-specific phospholipase C, as documented for alkaline phosphatase, acetylcholinesterase and Thy-1 antigen.
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PMID:Purification and characterization of a major glycoprotein in rat hepatoma plasma membranes. One of the membrane proteins released by phosphatidylinositol-specific phospholipase C. 303 62

The product of the c-fms proto-oncogene is related to, and possibly identical with, the receptor for the macrophage colony-stimulating factor, M-CSF (CSF-1). Unlike the product of the v-erbB oncogene, which is a truncated version of the EGF receptor, the glycoprotein encoded by the v-fms oncogene retains an intact extracellular ligand-binding domain so that cells transformed by v-fms express CSF-1 receptors at their surface. Although fibroblasts susceptible to transformation by v-fms generally produce CSF-1, v-fms-mediated transformation does not depend on an exogenous source of the growth factor, and neutralizing antibodies to CSF-1 do not affect the transformed phenotype. An alteration of the v-fms gene product at its extreme carboxyl-terminus represents the major structural difference between it and the c-fms-coded glycoprotein and may affect the tyrosine kinase activity of the v-fms-coded receptor. Consistent with this interpretation, tyrosine phosphorylation of the v-fms products in membranes was observed in the absence of CSF-1 and was not enhanced by addition of the murine growth factor. Cells transformed by v-fms have a constitutively elevated specific activity of a guanine nucleotide-dependent, phosphatidylinositol-4,5-diphosphate-specific phospholipase C. We speculate that the tyrosine kinase activity of the v-fms/c-fms gene products may be coupled to this phospholipase C, possibly through a G regulatory protein, thereby increasing phosphatidylinositol turnover and generating the intracellular second messengers diacylglycerol and inositol triphosphate.
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PMID:Transformation by the v-fms oncogene product: an analog of the CSF-1 receptor. 303 97

A number of plasma membrane glycoproteins of mammalian and protozoan origin are released from cells by phosphatidylinositol-specific phospholipase C. Some of these proteins have been shown to be attached to the lipid bilayer via a covalently linked, structurally complex glycophospholipid. Here we establish the existence of similarly linked glycoproteins in the yeast Saccharomyces cerevisiae. The most abundant of these is a tightly membrane-bound glycoprotein of 125 kd. The detergent-binding moiety of this protein can be removed by phosphatidylinositol-specific phospholipase C of bacterial origin or from Trypanosoma brucei. Metabolic labeling indicates that the protein contains covalently attached fatty acid and inositol. It also contains the cross-reacting determinant (CRD), an antigen found previously on the glycophospholipid anchor of protozoan and mammalian origin. Treatment of the protein with endoglycosidases F and H results in a 95-kd species. In the secretion mutant sec18, grown at 37 degrees C, the vesicular transport of glycoproteins is reversibly blocked between the rough endoplasmic reticulum and the Golgi apparatus. We find that sec18 cells, when grown at 37 degrees C, do add phospholipid anchors to newly synthesized glycoproteins. This indicates that these anchors are added in the rough endoplasmic reticulum.
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PMID:A major 125-kd membrane glycoprotein of Saccharomyces cerevisiae is attached to the lipid bilayer through an inositol-containing phospholipid. 304 36


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