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)

In rat cardiac sarcolemmal membranes a phosphoinositide-specific phospholipase C (PLC) was found to be present. The enzyme hydrolysed exogenous [3H-]phosphatidylinositol 4,5-biphosphate ([3H-]PtdIns(4,5)P2) in an optimized assay mixture containing 15 micrograms SL protein, 100 mM NaCl, 1 mM free Ca2+, 14 mM Na-cholate and 20 microM [3H-]PtdIns-(4,5)P2 (400-500 dpm/microliter) in 30 mM HEPES-Tris buffer (pH 7.0). The average specific activity was 9.14 +/- 0.55 nmol.mg-1.2.5 min-1. The addition of Mg2+ to the assay mixture did not change PLC activity but increased the relative amounts of dephosphorylated inositol products. In the absence of Na+ and at a low Ca2+ concentration (0.3 microM), Mg2+ also enhanced the intraSL levels of PtdIns4P and PtdIns, and, moreover, inhibited PLC activity (IC50-0.07 mM). PtdIns4P seemed to be a good substrate for th rat SL PLC (23.07 +/- 1.57 nmol.mg-1.2.5 min-1) whereas PtdIns was hydrolysed at a very low rate (0.36 +/- 0.08 nmol.mg-1.2.5 min-1). Unlike PtdIns(4,5)P2, PLC-dependent PtdIns4P and PtdIns hydrolysis was not inhibited by Ca2+ concentrations over 1 mM. The possibility of distinct isozymes being responsible for the different hydrolytic activities is discussed.
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PMID:The substrate specificity of phosphoinositide-phospholipase C in rat heart sarcolemma. 133 20

A fluorescent assay for Clostridium perfringens phospholipase C is described using 1-palmitoyl-2-[6(pyren-1-yl)hexanoyl]-sn-glycero-3- phospho-N-(trinitrophenyl)aminoethanol (PPHTE) as the substrate. This method is based on the decrease of the quenching of pyrene monomer fluorescence when phospholipase C hydrolyzes PPHTE into pyrenediglyceride and phospho(trinitrophenyl)-aminoethanol. The hydrolysis of egg lecithin/PPHTE (25:1 molar ratio) substrate by C. perfringens phospholipase C was linear with time for at least 2 min. Optimal conditions for the hydrolysis by phospholipase C were 50 mM Tris-HCl pH 7.0-30 mM CaCl2/63 microM egg lecithin and 2.5 microM PPHTE. The Km and Vmax values for the hydrolysis of egg lecithin/PPHTE vesicles were 28 microM and 280 pmol min-1, respectively. The detection limit of the assay was 40 microU of C. perfringens phospholipase C. When diglyceride was included into egg lecithin/PPHTE vesicles up to 30 mol% the reaction velocity increased 13-fold. Higher molar proportions of diglyceride were inhibitory. When the hydrolysis of mixtures of different naturally occurring phospholipids and PPHTE was studied egg lecithin was found to be the best substrate. When dipalmitoylphospholipids with different polar head groups were used the reaction velocity decreased in the order egg lecithin greater than or equal to dipalmitoylphosphatidylserine greater than dipalmitoylphosphatidic acid greater than dipalmitoylphosphatidylcholine greater than dipalmitoylphosphatidylglycerol.
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PMID:A continuous fluorometric assay for phospholipase C from Clostridium perfringens. 179 May 80

Alkaline phosphatase (ALP) activity has been demonstrated in periodontal ligament (PDL). On the basis of electron microscopic study, distribution of the enzyme in PDL tissue has also been indicated not only as a cell associated activity but also as an extracellular matrix associated activity. This study is concerned with the purification and characterization of the enzyme obtained from bovine PDL tissue. Purification of ALP extracted from the tissue included solubilization with 10 mM Tris-HCl buffer, pH 7.4, containing 0.2 mM MgCl2 and 0.1% Nonidet P-40 and fractionation by sequential chromatography utilizing DEAE-sephacel, Sepharose CL-6B and concanavalin A Sepharose 4B. Purity was established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This was followed by staining for ALP activity first with 2 mM beta-naphthyl acid phosphate and 1 mM Fast Blue BB Salt and then the protein with Coomassie Brilliant Blue. SDS-PAGE of the crude enzyme preparations gave a broad band with apparent molecular weight of 110,000-130,000 dalton. ALP activities were separated into two major peaks using Sepharose CL-6B chromatography. The void volume peak showed a purified form of 110,000 dalton ALP (110K ALP) while the second peak contained 120,000-130,000 dalton ALP (120-130K ALP) and other proteins. Sequentially, 120-130K ALP was purified by chromatography on concanavalin A Sepharose 4B. A polyclonal antibody was raised against purified bovine PDL 110K ALP in a rabbit. Immunodiffusion analysis showed that a polyclonal antibody against 110K ALP recognized 120-130K ALP. Analytical affinity chromatography on concanavalin A Sepharose 4B indicated that 110K ALP and 120-130K ALP had distinct affinity to the column which may depend upon the sugar chain structure. Digestion of 110K ALP with phosphatidylinositol-specific phospholipase C affected electrophoretic mobility but 120-130K ALP had no effect. It is suggested that 110K ALP is attached to a cell membrane anchored by a phosphatidylinositol glycan. In conclusion, bovine PDL contains two types of alkaline phosphatase i.e. 110K ALP and 120-130K ALP. Both ALPs are immunologically related although they have different sugar chain moieties. Furthermore, 110K ALP has a membrane anchoring domain. These results suggest that 110K ALP would be localized on the surface of the cell membrane and 120-130K ALP may associated with the extracellular matrix.
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PMID:[Purification and characterization of alkaline phosphatase obtained from bovine periodontal ligament]. 213 40

Qualitative and quantitative analyses were made to characterize the enzymatic degradation of sphingomyelin and phosphatidylcholine by midgut homogenates of the adult stable fly, Stomoxys calcitrans (L.). The results indicated that sphingomyelin was hydrolyzed by an enzyme with sphingomyelinase-like properties, and that phosphatidylcholine was hydrolyzed by an enzyme with properties similar to phospholipase C. The optimum pH for the sphingomyelinase was 7.6, and the rate of hydrolysis of sphingomyelin at that pH was linear from 1 to 4 nmol of substrate and 5 to 25 micrograms of enzyme preparation. Dialysis of the homogenates against Tris-HCl and imidazole buffers resulted in a decrease of sphingomyelinase activity by 59% and 98%, respectively, and the original activity was not restored with the addition of Ca++, Mg++, or Mn++.
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PMID:Hydrolysis of sphingomyelin and phosphatidylcholine by midgut homogenates of the stable fly. 213 66

The terminal differentiation of Schwann cells is dependent on contact with basement membrane. The present study was undertaken to investigate the role of cell surface heparan sulfate proteoglycans (HSPGs) in mediating Schwann cell responses to extracellular matrix contact. Phosphatidylinositol-specific phospholipase C-releasable cell surface HSPGs purified from cultures of neonatal rat Schwann cells were subjected to affinity chromatography on immobilized laminin and fibronectin. Binding of the HSPG to both affinity matrices was observed. The strength of the association, however, was sensitive to the ionic strength of the buffer. In 0.1 M Tris-HCl, HSPG binding was essentially irreversible whereas in physiological ionic strength buffer (e.g. 0.142 M NaCl, 10 mM Tris), weaker binding was detected as a delay in elution of the HSPG from the affinity columns. Further studies of HSPG-laminin binding suggested that the binding was mediated by the glycosaminoglycan chains of the proteoglycans. Results of equilibrium gel filtration chromatography provided additional evidence for a reversible association of the HSPG and laminin with a Kd of approximately 1 x 10(-6) M. When Schwann cells were plated on plastic dishes coated with laminin, the cells attached and extended long slender processes. Inclusion of heparin, but not chondroitin sulfate, in the assay medium resulted in partial inhibition of process extension, but at concentrations of heparin which were higher than that needed to disrupt laminin-HSPG association in vitro. Addition of anti-integrin receptor antibodies resulted in more extensive inhibition of laminin-dependent process extension. Anti-integrin antibodies plus heparin essentially totally inhibited laminin-dependent process extension. These results demonstrate that cell surface HSPGs are capable of reversible association with extracellular matrix molecules and suggest that HSPG-laminin interactions play a role in laminin-dependent Schwann cell spreading.
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PMID:Association of cell surface heparan sulfate proteoglycans of Schwann cells with extracellular matrix proteins. 224 8

The ability of 16 well-known cholinergic agonists to compete with 1 nM [3H]pirenzepine for the high (KH) and low (KL) affinity states of M1 muscarine receptors was studied, using rabbit hippocampal membranes suspended in 20 mM Tris buffer containing 1 mM MnCl2, at pH 7.4 and 25 degrees C. The hippocampus, like the cerebral cortex, has primarily m1 and m3 subtypes of M1 receptors; these receptors have very similar affinities for pirenzepine and for agonists, and both receptors are coupled to the activation of phospholipase C. KH values varied more than 10,000-fold, and did not correlate with prior measurements of the ability of agonists to promote cerebral excitation or phosphoinositide turnover in cortical tissue. KL values varied more than 1,000-fold, and also did not correlate with agonist activities. In contrast, KL/KH ratios for individual agonists varied from 66 for cis-dioxolane to near 1 for oxotremorine, and correlated closely with data concerning the relative physiological and biochemical effectiveness of the agonists. Each agonist showed only a single affinity in 0.2 mM guanyl-5'-yl imidodiphosphate. Thus binding measurements of KL/KH appear to be a new way to screen cholinergic agonists for relative efficacy at m1 or m3 receptors coupled to their native G proteins. Whereas both quaternary and tertiary agonists are known to activate M2 receptors, only the quaternary agents tested were highly effective M1 agonists. The five agonists which have been tested for improving human memory all appear to have low efficacy at M1 receptors.
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PMID:Affinities of different cholinergic agonists for the high and low affinity states of hippocampal M1 muscarine receptors. 253 65

Incubation of radiolabeled L-glutamic acid, a putative central excitatory neurotransmitter, in 50 mM Tris-acetate buffer (pH 7.4) at 30 degrees C in the absence of brain synaptic membranes resulted in a significant adsorption of the radioactivity to glass fiber filters routinely employed to trap the bound ligand in receptor binding assays. The adsorption was not only eliminated by the inclusion of L-isomers of structurally related amino acids, but also inhibited by that of most presumed agonists and antagonists for the brain glutamate receptors. This displaceable adsorption was a temperature-dependent nonreversible, and saturable phenomenon. Scatchard analysis of these data revealed that the adsorption consisted of a single component with an apparent dissociation constant of 73 nM. The displaceable adsorption was significantly attenuated by a concurrent incubation with papain, pronase E, and phospholipase C. A significant amount of the radioactivity was detected in the pass-through fraction of the Dowex column following an application of the reaction mixture incubated with purified [3H]glutamate at 30 degrees C for 60 min in the absence of membranous proteins added. Complete abolition of the displaceable adsorption resulted from the use of incubation buffer boiled at 100 degrees C as well as filtered through a nitrocellulose membrane filter with a pore size of 0.45 micron immediately before use. These results suggest that the displaceable adsorption may be attributable to the radioactive metabolite of [3H]glutamate by microorganisms contaminating the Tris-acetate buffer. This might in part contribute to some of the controversial results with regard to receptor binding studies on acidic amino acids.
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PMID:Microbial methodological artifacts in [3H]glutamate receptor binding assays. 254 31

A synthetic oligodeoxynucleotide probe was used to clone the gene encoding the phosphatidylcholine-preferring phospholipase C of Bacillus cereus. The sequence of a 2050-bp restriction fragment containing the gene was determined. Analysis of the gene-derived amino acid (aa) sequence showed that this exoenzyme is probably synthesized as a 283-aa precursor with a 24-aa signal peptide and a 14-aa propeptide. The mature, secreted enzyme comprises 245 aa residues. Sonicates of Escherichia coli HB101 carrying the gene on a multicopy plasmid showed phospholipase C activity. This activity was inhibited by Tris, a known inhibitor of the B. cereus enzyme and also by antiserum raised against pure B. cereus phospholipase C. We conclude therefore that the gene is expressed in E. coli. The cloning and sequencing described here complete the first step toward using in vitro mutagenesis for investigations of the structure-function relationships of B. cereus phospholipase C.
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PMID:Cloning and sequencing of the gene encoding the phosphatidylcholine-preferring phospholipase C of Bacillus cereus. 313 22

Phospholipase A has been solubilized from the sarcoplasmic reticulum of rat heart by treatment with Tris buffer, potassium chloride, taurodeoxycholate or octyl glucoside. On HPLC gel permeation, two phospholipases were identified at the void volume of a TSK 3000 column and at an apparent molecular mass of 60 kDa. The two activity peaks exhibited a predominance of phospholipase A1 activity (83-91%) and a lesser phospholipase C activity (4-9%) using sonicated 1-palmitoyl-2[1-14C]oleoylphosphatidylcholine liposomes as substrate. The voiding phospholipase A peak, which represented the bulk of the recovered activity, exhibited a requirement for calcium ions in the 0.3-3 microM range. The heat stability and response to mercuric ions was studied and some similarities were noted between the solubilized sarcoplasmic reticulum phospholipases A and the cytosolic phospholipases A of rat heart. It is speculated that the cytosolic phospholipase A which we reported earlier may represent in part phospholipase A released from sarcoplasmic reticulum during isolation of the subcellular membrane fractions.
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PMID:Solubilization and partial characterization of phospholipase A from rat heart sarcoplasmic reticulum. 316 81

Heat treatment of a wild-type Escherichia coli strain at 55 degrees C in 50 mM Tris-hydrochloride buffer with or without 10 mM magnesium sulfate or HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) buffer at pH 8.0 caused an increase in cell surface hydrophobicity. By determining the location of n-hexadecane droplets attached to cells by phase-contrast microscopy, the septal and polar regions of heated cells appeared to become the most frequently hydrophobic. Some of the lipopolysaccharide molecules in the outer membrane were released from heated cells, and the cells became susceptible to the hydrolytic action of added phospholipase C. Heat-treated cells also became permeable to the hydrophobic dye crystal violet, which was added externally. The release of part of the outer membrane by heat treatment appeared to bring about the disorganization of the outer membrane structure and, as a consequence, to result in the partial disruption of the permeability barrier function of the outer membrane. Tris was found to enhance damage to the outer membrane by heat.
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PMID:Destruction of the outer membrane permeability barrier of Escherichia coli by heat treatment. 390 17


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