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)

Mechanical loading alters the metabolism of articular cartilage, possibly due to effects of shear stress on chondrocytes. In cultured chondrocytes, glycosaminoglycan synthesis increases in response to fluid-induced shear. This study tested the hypothesis that shear stress increases nitric oxide production in chondrocytes, and nitric oxide then influences glycosaminoglycan metabolism. Inhibitors of nitric oxide synthase, G proteins, phospholipase C, potassium channels, and calcium channels were also analyzed for effects on nitric oxide release and glycosaminoglycan synthesis. Fluid-induced shear was applied to primary high-density monolayer cultures of adult bovine articular chondrocytes using a cone viscometer. Nitric oxide release in chondrocytes increased in response to the duration and the magnitude of the fluid-induced shear. Shear-induced nitric oxide production was reduced in the presence of nitric oxide synthase inhibitors-but was unaffected by pertussis toxin, neomycin, tetraethyl ammonium chloride, or verapamil. The increase in glycosaminoglycan synthesis in response to shear stress was blocked by nitric oxide synthase inhibitors, pertussis toxin, and neomycin but not by tetraethyl ammonium chloride or verapamil. The phospholipase C inhibitor, neomycin, also decreased glycosaminoglycan synthesis in the absence of flow-induced shear. As studied here, shear stress increased nitric oxide production by chondrocytes, and the shear-induced change in matrix macromolecule metabolism was influenced by nitric oxide synthesis, G protein activation, and phospholipase C activation.
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PMID:Nitric oxide and G proteins mediate the response of bovine articular chondrocytes to fluid-induced shear. 906 31

Neuronal nitric oxide synthase (nNOS; EC 1.14.13.39) activity in supernatant of rat cerebellum homogenate was unstable and chelating reagent protected the activity from the rapid decrease. The main target ion of the chelating reagent was found to be Ca2+. Although the enzyme was very unstable after purification by the procedures including DEAE-cellulose chromatography and ammonium sulfate precipitation, the inactivation was neither accelerated by addition of Ca2+ nor protected by EGTA. Upon addition of boiled supernatant of rat cerebellum homogenate, this purified enzyme became more active and stable, but rapid inactivation occurred again by addition of Ca2+, suggesting the existence of previously unreported Ca2(+)-dependent stabilizer / activator in the boiled supernatant. This factor was concentrated by organic solvent and the effects on the enzyme were completely canceled by addition of Ca2+ or phospholipase C treatment.
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PMID:Calcium-dependent inactivation of neuronal nitric oxide synthase: evidence for the existence of stabilization / activation factor. 917 96

An arginine-specific ADP-ribosyltransferase activity was detected in chicken spleen membrane fraction using a capillary electrophoresis assay and the activity was extracted by phosphatidylinositol-specific phospholipase C but not by 1 M NaCl or 1% Triton X-100. The enzyme protein was purified from chicken spleen membrane fraction to apparent homogeneity with a six-step method containing phosphatidylinositol-specific phospholipase C treatment, ammonium sulfate precipitation and conventional column chromatographies. Apparent molecular mass of the purified enzyme estimated with SDS/PAGE was 44 kDa. N-glycanase treatment of the enzyme reduced the apparent molecular size on SDS/PAGE. The enzyme was recognized by anti-cross reacting determinant antibodies. Partial amino acid sequence of the purified enzyme protein showed high homologies with primary structures of previously reported chicken arginine-specific ADP-ribosyltransferases.
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PMID:A newly identified glycosylphosphatidylinositol-anchored arginine-specific ADP-ribosyltransferase in chicken spleen. 919 60

The aim of the present work was to study the effect of the atrial natriuretic factor (ANF) on the Na/H antiport in rat aorta smooth muscle cells, evaluated as intracellular pH (pHi) recovery after an acid load with ammonium chloride. The Na/H antiport was studied using a fluorescent probe, sensitive to pHi, 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Our data indicate that ANF modulates the activity of the Na/H antiport in both a dose- and time-dependent manner. Hormone concentrations of 10(-10) M activate the antiport, increasing both the rate of recovery and the set point by approximately 0.2 pH units. This effect is mediated by diacylglycerol as a result of phospholipid hydrolysis by a phospholipase C, even if an involvement of adenosine 3',5'-cyclic monophosphate (cAMP) cannot be ruled out. ANF (10(-7) M) inhibits the antiport, decreasing both the rate of recovery and the set point by approximately 0.3 pH units, because of guanosine 3',5'-cyclic monophosphate production. Both inhibition and stimulation of pHi by ANF were more pronounced when the hormone was given before the acid load, perhaps because of the longer time exposure. We present new hypotheses on the mechanism of action of this paracrine/autocrine factor.
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PMID:Dual modulation of Na/H antiport by atrial natriuretic factor in rat aortic smooth muscle cells. 927 62

The kinetic parameters of the phosphatidylcholine-preferring phospholipase C from Bacillus cereus (PLCBc) have been evaluated for phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine substrates with a new assay based on the quantitation of inorganic phosphate (Pi). Treatment of the phosphomonoester product of the PLCBc-catalyzed hydrolysis of these phospholipids with alkaline phosphatase releases Pi. This Pi forms a complex with ammonium molybdate that is then reduced by ascorbic acid to provide a blue molybdenum chromogen with an absorbance maximum at 700 nm. This highly sensitive assay may be used to determine accurately less than 5 nmol of Pi in solution. Performing the assay in 96-well plates provides a rapid and convenient method to evaluate a variety of phospholipids as substrates for PLCBc. The assay has been utilized to ascertain the kinetic constants for the PLCBc-catalyzed hydrolysis of 1,2-dihexanoyl-sn-glycero-3-phosphocholine, 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine, and 1,2-dihexanoyl-sn-glycero-3-phospho-L-serine. It is found that these compounds are substrates for the enzyme with their VmaxS being in the order of phosphatidylcholine > phosphatidylethanolamine > phosphatidylserine.
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PMID:Determination of the kinetic parameters for phospholipase C (Bacillus cereus) on different phospholipid substrates using a chromogenic assay based on the quantitation of inorganic phosphate. 930 81

The in vitro postantibiotic effect (PAE) and the postantibiotic effect of subinhibitory concentrations (PA SME) of gentamicin were investigated on clinical isolates of Salmonella typhimurium, Salmonella enteritidis and Pseudomonas aeruginosa. The PAE was induced by 2 x MIC and 4 x MIC of gentamicin for 0.5 h. The PA SME were studied by the addition of 0.1, 0.2 and 0.3 x MIC during the postantibiotic phase of the bacteria. The S. enteritidis strain did no regrow after affecting of supra-subinhibitory concentrations for 24 h with exception of the concentration 2 x MIC + 0.1 x MIC. The PAEs against P. aeruginosa were nearly identical for all the suprainhibitory concentrations tested (4.4-4.6 h) and no regrowth after PA SME was observed. The studied pharmacodynamic parameters decreased the surface hydrophobicity of Salmonella sp., mainly of S. enteritidis, evaluated by the ability to bind Congo red and by the aggregation in solutions of ammonium sulphate (SAT). Gentamicin in suprainhibitory concentrations expressively decreased the phospholipase C production--an important virulence factor of P. aeruginosa.
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PMID:Pharmacodynamic parameters of gentamicin and their effect on biological properties of gram-negative bacteria. 947 60

Cell pH was monitored in medullary thick ascending limbs to determine effects of ANG II on Na(+)-K+(NH4+)-2Cl- cotransport. ANG II at 10(-16) to 10(-12) M inhibited 30-50% (P < 0.005), but higher ANG II concentrations were stimulatory compared with the 10(-12) M ANG II level cotransport activity; eventually, 10(-6) M ANG II stimulated 34% cotransport activity (P < 0.003). Inhibition by 10(-12) M ANG II was abolished by phospholipase C (PLC), diacylglycerol lipase, or cytochrome P-450-dependent monooxygenase blockade; 10(-12) M ANG II had no effect additive to inhibition by 20-hydroxyeicosatetranoic acid (20-HETE). Stimulation by 10(-6) M ANG II was abolished by PLC and protein kinase C (PKC) blockade and was partially suppressed when the rise in cytosolic Ca2+ was prevented. All ANG II effects were abolished by DUP-753 (losartan) but not by PD-123319. Thus < or = 10(-12) M ANG II inhibits via 20-HETE, whereas > or = 5 x 10(-11) M ANG II stimulates via PKC Na(+)-K+(NH4+)-2Cl- cotransport; all ANG II effects involve AT1 receptors and PLC activation.
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PMID:ANG II controls Na(+)-K+(NH4+)-2Cl- cotransport via 20-HETE and PKC in medullary thick ascending limb. 957 2

The novel phospholipid 2, which bears a tert-butyl moiety in place of the natural trimethyl ammonium group of phosphatidylcholine, has been enzymatically synthesized via a transphosphatidylation reaction mediated by phospholipase D. The change from the choline headgroup in 1 to the tert-butyl group in 2 reduced the efficiency of hydrolysis by the phosphatidylcholine-preferring phospholipase C from Bacillus cereus by a factor of greater than 10(3).
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PMID:Enzymatic synthesis of a modified phospholipid and its evaluation as a substrate for B. cereus phospholipase C. 987 66

Microglial cells are thought to serve as sensors for pathologic events in the brain. In the present study we demonstrate that these cells respond with an increase in intracellular calcium concentration ([Ca2+]i) to intracellular alkaline shifts induced by either application of NH3/NH4+ or by an extracellular alkaline shift. The cytoplasmic pH (pHi) and [Ca2+]i in cultured mouse microglial cells were studied employing the fluorescent probes BCECF and fura-2, respectively. Application of NH3/NH4+ caused an initial rapid alkalinization followed by a slow recovery towards the resting level, while application of alkaline (pH 8.2) solution triggered a slower rise in pHi. The [Ca2+]i elevation triggered by NH3/NH4+ and extracellular alkaline shift were caused by different mechanisms: extracellular alkalinization induced a transmembrane Ca2+ entry, whereas NH3/NH4+ triggered Ca2+ release from thapsigargin- and ATP-sensitive intracellular pools. The mobilization of intracellular Ca2+ caused by NH3/NH4+ was blocked by a specific inhibitor of phospholipase C, U-73122, but was not affected by an inhibitor of G-protein, pertussis toxin. This implies that NH3/NH4 interacts with phospholipase C and leads to an increase in the intracellular level of inositol 1,4,5-trisphosphate (InsP3). In contrast to a previous study using a microglial cell line, application of NH3/NH4+ did not result in a release of tumor necrosis factor alpha (TNF-alpha), a marker of microglial activation, in the primary microglial cells. This implies that ammonium does not lead to activation of microglia in the culture model.
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PMID:Ammonium triggers calcium elevation in cultured mouse microglial cells by initiating Ca(2+) release from thapsigargin-sensitive intracellular stores. 1065 Sep 90

Melanotransferrin (MTf) is a membrane-bound transferrin (Tf) homologue with several characteristics in common with serum Tf. MTf is found at high levels in melanoma cells and previous studies have shown that MTf can bind Fe. In addition, Chinese hamster ovary cells transfected with MTf transport Fe from 59Fe-citrate at greater rates than control cells. However, the role of MTf in the Fe uptake process of human melanoma cells remains unknown. In the present study we have characterized the role of MTf in Fe uptake by SK-Mel-28 melanoma cells in order to understand its function. Initial studies examined whether modulation of intracellular Fe levels using the Fe chelator desferrioxamine (DFO) or the Fe donor ferric ammonium citrate (FAC) could change MTf mRNA levels. In contrast to transferrin receptor (TfR) mRNA that increased after exposure to DFO and decreased after incubation with FAC, there was no change in MTf mRNA levels. In addition, compared to control cells, there was no alteration of 125I-labelled anti-MTf mAb-binding in cells exposed to DFO or FAC, suggesting no change in the number of MTf sites. Further studies examined the ability of DFO and FAC to modulate Fe uptake from 59Fe-citrate which is bound by MTf. In contrast to the effect of DFO or FAC at increasing and decreasing Fe uptake from 59Fe-Tf, respectively, DFO had no influence on 59Fe-citrate uptake, whereas FAC markedly increased it. Collectively, these studies suggest that MTf is not regulated in a manner similar to the TfR in response to cellular Fe levels. MTf can be removed from the membrane by phosphatidylinositol-specific phospholipase C (PtdIns-PLC). Preincubation of melanoma cells with PtdIns-PLC reduced anti-MTf mAb binding to 3% of the control, while PtdIns-PLC only slightly reduced 59Fe uptake from 59Fe-citrate. These results suggest that MTf played only a minor role in Fe uptake from 59Fe-citrate by these cells. The expression of MTf mRNA (poly A+) was also examined in 50 human tissues and found to be markedly different to Tf mRNA or TfR mRNA. Surprisingly, MTf mRNA expression was widespread in normal tissues, and was observed at its highest levels in the salivary gland. In contrast to expectations, MTf mRNA expression was generally greater in adult than fetal tissues.
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PMID:The role of the membrane-bound tumour antigen, melanotransferrin (p97), in iron uptake by the human malignant melanoma cell. 1069 65


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