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)

Lipid micelles were prepared by incubating a mixture of glycerides (triolein, diolein, and monoolein), and lecithin in Krebs-Ringer phosphate buffer at 37 degrees C for 30 min. It was found that adrenaline stimulated the release of free fatty acids in a lipolytic system consisting of the lipid micelles and adipose tissue lipase. Adrenaline did not increase the cyclic AMP content of the reaction mixture. Dibutyryl cyclic AMP, theophylline, and phospholipase C increased the rate of lipolysis in the system but cyclic AMP and phospholipase D did not.
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PMID:Studies on adrenaline-induced lipolysis in artificial lipid micelles. 1 41

The disruption of the molecular organization of the plasma membrane of leukocytes by phagocytosable particles, or by agents such as surfactants, antibodies, phospholipase C, fatty acids and chemotactic factors, leads to a stimulation of the phagocyte oxidative metabolism. Concanavalin A (Con A) has been used as a tool to study the mechanism of this metabolic regulation. The binding of Con A to the surface of polymorphonuclear leukocytes (PMNL) or macrophages produces a rapid enhancement of oxygen uptake and glucose oxidation through the hexose monophosphate pathway (HMP). This is explained by an activation of the granular NADPH oxidase, the key enzyme in the metabolic stimulation. The effect of Con A is not due to endocytosed lectin, since Con A covalently coupled to large sepharose beads still acts as stimulant. The metabolic changes caused by Con A are reversible. If, after the onset of stimulation, sugars with high affinity for Con A are added to the leukocyte suspension, the activity of granular NADPH oxidase and the rate of respiration and glucose oxidation return to their resting values. The metabolic burst, while partially supressed by treatment of PMNL with iodoacetate, sodium flouride and cytochalasin B, is slightly increased by colchicine. Con A induces a selective release of granular enzymes (beta-glucuronidase, peroxidase, alkaline phosphatase) from PMNL, whereas no leakage of cytoplasmic enzymes is observed. The enzyme release is inhibited by iodoacetate and by drugs known to increase cell levels of cyclic AMP. Based on a current view of the mode of interaction between Con A and cell surfaces, a model of the metabolic disruption of leukocytes is presented.
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PMID:Concanavalin A as a probe for studying the mechanism of metabolic stimulation of leukocytes. 16 45

The possible effects of phospholipase A and phospholipase C on the rate of uridine incorporation into RNA in mammary gland explants of mice were tested. Phospholipase C had no effect on the rate of uridine incorporation, but it did suppress the action of prolactin on this metabolic parameter. In contrast, phospholipase A was found to stimulate the rate of uridine incorporation into RNA in a manner similar to that of prolactin. The time-courses for the onset of the prolactin and phospholipase A effects were the same. Also, the phospholipase A effect was nonadditive to the effect produced by a maximally stimulatory concentration of prolactin. Finally it was observed that, like the prolactin effect, the phospholipase A effect was abolished by incubation with dibutyryl cyclic AMP, theophylline, quinine, indomethacin and prostaglandin E1. Further, the phospholipase A effect was nonadditive to the prolactin-like effects produced by the cyclic GMP, prostaglandin F2alpha or arachidonic acid. These data therefore suggest that prolactin and phospholipase A stimulate RNA synthesis in mammary gland explants via similar processes.
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PMID:Phospholipases and the effect of prolactin on uridine incorporation into RNA in mammary gland explants of mice. 17 86

WISH cells grown in vitro were pretreated with subcytotoxic concentrations of digitonin, cortisol and purified bacterial toxins -- staphylococcal beta-haemolysin or Clostridium perfringens alpha-toxin and irradiated with 3 GHz electromagnetic wave (microwaves) at the field power densities 5 or 40 mW/cm2. At 40 mW/cm2 increase in temperature of the culture medium of about 2-3 degrees C was noted, while at 5 mW/cm2 no detectable increase in temperature was found. Control and pretreated WISH cells after irradiation in the microwave field were used for evaluation of their viability, incorporation of tritiated thymidine, glycine and uridine and level of intracellular cyclic AMP. Irradiation with microwaves resulted in lowering of thymidine and glycine incorporation along with changes in the intracellular amount of cAMP (decrease in cells exposed to 5 mW/cm2 and increase in those exposed to 40 mW/cm2). Under both conditions viability of the cultures was normal. Pretreatment of cells with digitonin or purified bacterial toxins followed by irradiation with microwaves resulted in enhancement of the cytotoxic effect with lowering of cell viability, especially after exposition to power density of 40 mW/cm2. Cortisol led to decrease in 3H-glycine and 3H-uridine incorporation into WISH cells, but did not influence the reaction of the cells to microwave radiation. In view of the results presented it may be concluded that substances injuring cell membranes sensitize cell cultures to electromagnetic radiation of the microwave range and may enhance the specific (non-thermal) effect of microwaves.
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PMID:Effect of microwave radiation on cells treated with membrane-injuring substances. 20 Apr 52

Purified phospholipae C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) and theta-toxin from Clostridium perfringens both inhibited noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes in a dose-dependent manner. The action of phospholipase C was gradual in onset, while the effect of theta-toxin was almost immediate. Phospholipase C, but not theta-toxin, hydrolyzed membrane phospholipids and inhibited adenylate cyclase (EC 4.6.1.1) in a crude membrane fraction from fat cells. The inhibitory effects of phospholipase C were associated with morphological alterations detectable by electron microscopy, whereas effects of theta-toxin were observed at a time when no clearcut morphological alterations could be observed. It is concluded that the two purified principles from C. perfringens, which are both present in commercial preparations of phospholipase C, antagonize noradrenaline-stimulated cyclic AMP accumulation and lipolysis. Although their exact mechanisms of action have not been elucidated, phospholipase C and theta-toxin have different modes of attack.
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PMID:Inhibition of noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes by purified phospholipase C and theta-toxin from Clostridium perfringens. 20 64

Possible interactions between polymerized (F-) actin and insulin-storage granules from rat islets of Langerhans were examined in vitro by comparing the sedimentation of the granules in the presence of various actin concentrations. Actin in the concentration range 0.1--0.5 mg/ml produced a retardation in granule-sedimentation rates consistent with binding of the granules to the actin filaments. The interaction was increased by addition of ATP (2mM), but was decreased by CaCl2 (0.1 mM). Binding of granules to actin was unaffected by cyclic AMP or by preincubation of the granules with phospholipase C. Specificity of the interaction was confirmed by the use of depolymerized (G-) actin and of myosin to provide a solution of comparable viscosity; neither of these caused any alteration of granule sedimentation. Possible implications of this interaction of insulin-storage granules with actin for the mechanism of insulin secretion are briefly discussed.
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PMID:Interaction between insulin-storage granules and F-actin in vitro. 22 Sep 62

The effect of a lethal toxic fragment of staphylococcal alpha-toxin on the activity of adenosine 3',5'-monophosphate(cyclic AMP)-dependent protein kinase was examined. 1. The lethal toxic fragment produced a dose-dependent decrease in both the binding of cyclic AMP to the regulatory subunit and phosphorylation activity of cyclic AMP-dependent protein kinase obtained from rabbit skeletal muscles up to a plateau at a 50% inhibitory effect. The decrease in the activity of protein kinase observed with low doses of the lethal toxic fragment (0.1 microM) resulted from a competitive inhibition, probably by its interaction with the cyclic AMP-binding site in the regulatory subunit molecule. 2. The effects of a lethal toxic fragment and epinephrine on the cyclic AMP level and protein kinase activity were investigated in the perfused rabbit heart slices. The lethal toxic fragment attenuated the stimulation of cyclic AMP-dependent protein kinase activity ratio by epinephrine. 3. It is suggested that the specific action of a lethal toxic fragment on the cellular membrane enzymes may be attributable to the inhibition of the cyclic AMP-dependent protein kinase activity.
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PMID:Inhibitory effect of a lethal toxic fragment of staphylococcal alpha-toxin on cyclic AMP-dependent protein kinase activity. 22 66

Cyclic AMP-dependent protein kinases from several mammalian sources inhibit Na+-dependent alpha-aminoisobutyric acid transport by membrane vesicles isolated from 3T3 cells. Evidence is provided that phosphorylation of membrane proteins by the enzyme is responsible for the inhibition. Lysis of the vesicles, or a reduction in the intravesicular volume is not the cause of reduced transport. The cyclic AMP-dependent protein kinase and its catalytic subunit phosphorylate a number of membrane proteins. Most of these proteins are phosphorylated, but to a lesser extent in the absence of protein kinase or cyclic AMP. The phosphorylated proteins remain associated with the membranes during hypotonic lysis treatments, which would be expected to release intravesicular contents and loosely associated membrane proteins. 32P-labeled bands detected on sodium dodecyl sulfate polyacrylamide gels after phosphorylation of membranes by the catalytic subunit of the cyclic AMP-dependent kinase are eliminated by treatment with either pronase or 1 N NaOH, but not by ribonuclease nor by phospholipase C. The stability of the incorporated radioactivity to hot acid and hydroxylamine relative to hot base suggests that most of the 32P from [gamma-32P]ATP is incorporated into protein phosphomonoester linkages.
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PMID:Inhibition of alpha-aminoisobutyric acid transport in membrane vesicles from mouse fibroblasts after phosphorylation by cyclic AMP-dependent protein kinase. 22 60

The 5'-nucleotidase localized in rat liver plasma membranes was purified to a single protein, which contained phospholipid. The molecular weight and the sedimentation constant were about 150 000 and 7 S in the presence of sodium deoxycholate, while the enzyme protein was aggregated when the preparation was dialyzed thoroughly. The purified 5'-nucleotidase exhibited the same properties as the 5'-nucleotidase in plasma membranes. The 5'-nucleotidase activity was increased by the addition of various bile salts or by the solubilization of membranes with trypsin, papain or phospholipase C. The solubilized and aggregated forms of the enzyme showed different substrate specificity for nucleotides, pH optimum, heat stability and Km. The purified enzyme catalyzed an exchange reaction between AMP and adenosine, which was diminished by the addition of sodium deoxycholate.
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PMID:Effect of sodium deoxycholate on 5'-nucleotidase. 125 10

Thrombin is thought to stimulate responsive cells by cleaving cell-surface receptors coupled to intracellular second-messenger-generating enzymes via G-proteins. In order to understand this process better, we have examined the regulation of adenylate cyclase by thrombin in the megakaryoblastic HEL cell line and compared it with platelets. A notable difference was found. In HEL-cell membrane preparations, thrombin inhibited cyclic AMP (cAMP) formation by a pertussis-toxin-sensitive mechanism comparable with that observed in platelets. In contrast, when added to intact HEL cells, thrombin activated adenylate cyclase and caused an increase in cAMP formation synergistic with that produced by forskolin and prostaglandin I2. This increase, which was not seen with platelets, was accompanied by an increase in cAMP metabolism by phosphodiesterase. Like other responses to thrombin, the increase in cAMP formation required proteolytically active thrombin and was subject to homologous desensitization. An equivalent response could be evoked by the addition of a polypeptide, derived from the N-terminus of the thrombin receptor, that has been shown to activate the receptor. The effects of thrombin could not, however, be reproduced by the addition of phorbol ester and the Ca2+ ionophore, A23187, nor be prevented with inhibitors of arachidonate metabolism. Preincubation of the cells with adrenaline, which inhibited Gs-mediated activation of adenylate cyclase, or pertussis toxin, which inhibited phospholipase C activation, had no effect on thrombin-induced cAMP formation. These results suggest that thrombin can regulate cAMP formation by two different mechanisms. First, thrombin can inhibit adenylate cyclase in a Gi-dependent manner. This effect predominates in HEL-cell membrane preparations, as it does in platelets, but is not detectable when thrombin is added to intact HEL cells. Instead, in intact HEL cells thrombin activates adenylate cyclase. Although clearly receptor-mediated, this response does not appear to involve Gi, Gs, protein kinase C, eicosanoid formation or changes in the cytosolic Ca2+ concentration.
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PMID:Dual regulation of cyclic AMP formation by thrombin in HEL cells, a leukaemic cell line with megakaryocytic properties. 131 10


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