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)

Substantial thrombomodulin activity could be detected in tissue thromboplastin preparations from placenta or from lung but not from brain. When the amount of these preparations was adjusted to contain 1 unit of tissue factor activity, up to 0.85 units of thrombomodulin activity could be measured, corresponding to the generation of 17 pmol/ml/min of activated protein C when 1.5 microM human protein C was activated by 20 nM human alpha-thrombin in the presence of 5 mM CaCl2. After treatment by phospholipase C, thrombomodulin activity was reduced in these samples. Addition of mixed brain procoagulant phospholipids partially restored thrombomodulin activity in the phospholipase C-treated samples. These results emphasize the role of phospholipids in the expression of optimal thrombomodulin activity in tissue thromboplastin preparations from placenta or from lung.
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PMID:Thrombomodulin activity is found in tissue thromboplastin preparations from placenta and from lung but not from brain. 303 9

Incubation of bacterial cells in 0.1 M CaCl2 at 0 degrees C considerably increases the amount of phospholipids susceptible to action of a specific enzyme of phospholipid metabolism phospholipase C (hydrolysis to diacylglycerides). In process of incubation in CaCl2 solutions at 0 degrees C the expressed activity of an endogenous enzyme phospholipase A has been registered in cellular samples. Binding of the enzyme by the cells under conditions unfavourable for phospholipids hydrolysis (0 degrees C) suppresses strongly and reversibly cellular ability to DNA transformation without affecting cellular survival. As calculated, the enzyme molecules cover about 10% of cellular surface while inhibiting 90% of transmembrane transfer. The obtained data are considered to be a solid argument supporting the important role of the membrane phospholipids in the mechanism of cation-induced DNA transfer into the cell.
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PMID:[Effect of phospholipase on cation-induced transmembrane transport of DNA in Escherichia coli]. 304 11

Incubation of washed human sperm with [3H]- or [14C]arachidonic acid allowed a major incorporation of the label into phospholipids, provided that the final concentration of the fatty acid did not exceed 20 microM. A further challenge with calcium ionophore A23187 of spermatozoa suspended in a calcium-containing medium led to phospholipid hydrolysis, which could account for 10-12% of total cell radioactivity. Degradation products were identified as free, unconverted arachidonic acid, occurring with some diacylglycerol. Phospholipid hydrolysis was significant after 15 min of incubation and became maximal after 120 min. It was found to be calcium dependent, diacylglycerol and free arachidonate production occurring maximally at 2 mM and 5 mM CaCl2, respectively. Phosphatidylcholine and phosphatidylinositol were the most significantly degraded phospholipids after 60 min of incubation. Similar incubations conducted with 32P-labeled sperm confirmed the selective hydrolysis of phosphatidylcholine and revealed an increase production of phosphatidic acid probably due to a phosphorylation of diacylglycerol. Under the same conditions, one third of the cells remained motile and electron microscopy revealed that acrosome reaction was completed in 40% of the cells and displayed an intermediary state in 40-50% of the spermatozoa. Furthermore, a good parallelism was observed between the extent of the acrosome reaction and the extent of phospholipid hydrolysis promoted by increasing concentrations of A23187. It is concluded that calcium entry into the cells activates both a phospholipase A2 and a phospholipase C, leading to the production of substances, like lysophospholipid, diacylglycerol or phosphatidic acid, which may or may not be involved in acrosome reaction.
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PMID:Evidence for the activation of phospholipases during acrosome reaction of human sperm elicited by calcium ionophore A23187. 310 92

The early events in staphylococcal alpha-toxin action on mouse adrenocortical (Y1) tumor cells were studied. Cell-bound toxin could be partially neutralized by anti-alpha-toxin and inactivated by trypsin added within 10 min at 37 degrees C after the end of the binding step. Likewise, cell-bound toxin was capable of lysing rabbit erythrocytes (RRBC) added to the cells within 10 min after binding at 37 degrees C. After this time, the Y1 cells could not be rescued from intoxication by antibodies or trypsin, and the toxin was not accessible for lysis of RRBC. However, at 0 to 4 degrees C, the cell-bound toxin remained accessible to antibodies for at least 4 h. CaCl2 (30 mM) did not affect binding of the toxin to Y1 cells but completely prevented the intoxication if added within 10 min at 37 degrees C after the end of the binding step. The intoxication was independent of metabolic energy, active receptor clustering on the cell surface, and endocytosis of the toxin. Therefore, alpha-toxin interacted with the Y1 cell membrane in at least three separable steps: binding, a conformational change at the cell surface, and membrane damage. These early events appear to be similar to those occurring on RRBC treated with alpha-toxin.
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PMID:Early events in the action of staphylococcal alpha-toxin on the plasma membrane of adrenocortical Y1 tumor cells. 374 56

Calcium in millimolar concentrations protected rabbit erythrocytes from hemolysis caused by staphylococcal alpha-toxin. This effect was maximal at 30 mM CaCl2 and required the continued presence of calcium. The protection was not absolute and could be overcome by increased concentrations of alpha-toxin. Calcium did not block the binding of alpha-toxin to erythrocytes but inhibited the alpha-toxin-induced release of small ions from the cell as measured by 86Rb release. The transient removal of calcium was sufficient to abrogate its protective effect, suggesting that its action involves a reversible alteration in the state of the membrane. The three steps of the alpha-toxin-induced hemolytic sequence are: (i) binding to specific receptors, (ii) formation of transmembrane pores, and (iii) cell lysis. We concluded that calcium acted at step ii by impeding the lateral movement of alpha-toxin necessary to form the transmembrane hexamer pores.
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PMID:Effect of calcium ions on staphylococcal alpha-toxin-induced hemolysis of rabbit erythrocytes. 396 8

The properties of adult rhesus monkey testicular FSH receptor was investigated in these experiments. The interaction of 125I-labeled human FSH with a monkey testicular particulate fraction is a time- and temperature dependent phenomenon. Equilibrium of hormone-receptor interaction occurred by about 4-6 at 37 or 34 C, was slow at 25 C, and was extremely slow at 4 C. Maximum binding occurred at pH 7-7.5, with a requirement of 5-10 mM MgCl2 or CaCl2. The half-life of the receptor with exposed sites for hormone interaction was temperature related (1 h at 37 C, 1.5 h at 34 C, 6 h at 25 C, and 36 h at 4 C). Occupancy of these sites by the labeled hormone rendered the receptor more stable. The hormone-receptor complex was highly stable, as shown by the fact that excess unlabeled hormone was unable to displace the already bound labeled hormone from the receptor. Conditions unfavorable for hormone-receptor interaction, such as pH 5.0 or pH 10 or high salt concentration (0.5 M MgCl2), induced the maximum dissociation of the preformed hormone-receptor complex. The primate testis FSH receptor was inactivated by trypsin, phospholipase C, and reducing agents, but it was not influenced by nucleases. Neuraminidase treatment of the particulate receptor may have enhanced its ability to bind labeled human FSH.
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PMID:Studies on primate gonadotropin receptors: characterization of the rhesus monkey testicular follicle-stimulating hormone receptors. 629 May 23

Electron spin resonance (ESR) and the spin label method, with 5-doxyl stearic acid as a probe, were used to investigate the structure of microvillus membrane (MVM) from small intestine of adult and newborn rats. It was shown that the spin label in MVM of newborn was maintained in a more disordered environment than the spin label in adult animals. Calcium ion was used as an external stimulus to study the structural response and organization of these two membrane preparations. Ca++ enhanced the order of 5-doxyl stearic acid labeled MVM from mature and immature rats in a concentration-dependent saturable process, but Ca++ exerted a greater ordering effect on MVM from immature than MVM from the mature rat. Ca++ binding to MVM was also a concentration-dependent, saturable process. MVM from immature rat bound significantly more Ca++ in CaCl2 concentration ranges from 12.5 micron to 4mM. Scatchard analysis of the binding data showed two classes of binding sites with a high affinity constant of 3.1 X 10(4) M-1 and a low affinity constant of 9.1 X 10(3) M-1, with corresponding maximum binding capacities for each class site of 129.8 nmole of calcium/mg protein and 252.7 nmole calcium/mg of protein in newborn and 13-day-old MVM. Only one high affinity constant of 2.6 X 10(4)M-1 with a corresponding maximum binding capacity of 106.4 nmole/mg of protein was observed in adult MVM. Proteolytic hydrolysis of the membranes by trypsin produced an increase in Ca++ binding in adult MVM and a decrease in Ca++ binding in newborn MVM. Neuraminidase and phospholipase C reduced the amount of bound Ca++ in both adult and newborn MVM. These results indicate a more disordered structure of newborn MVM and a differential effect of Ca++ on MVM during development.
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PMID:Development of the gastrointestinal mucosal barrier V. Comparative effect of calcium binding on microvillus membrane structure in newborn and adult rats. 631 42

Phospholipase C activity capable of hydrolysing phosphatidylinositol in bovine heart was resolved into four forms (I-IV) by ion-exchange chromatography. Some of these forms could only be detected if the assay was performed at acidic pH (I and IV) or in the presence of deoxycholate (II). Gel-filtration chromatography indicated that the four forms had different molecular weights in the range 40000-120000. I, II and III all had pH optima in the range 4.5-5.5. However, the major form (III) also had substantial activity at pH 7.0 and above. The activities of I, II and III at pH 7.0 were stimulated by deoxycholate; this effect was most marked with I and II, which had very low activity at this pH. All forms of the enzyme were inhibited by EGTA and required 2-5 mM-CaCl2 for maximal activity. When the fractions eluted from the ion-exchange and gel-filtration columns were assayed with polyphosphoinositides as substrates there was a close correspondence to the elution profile obtained with phosphatidylinositol as substrate; there was no evidence for the existence in heart of phospholipase C activities specific for individual phosphoinositides.
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PMID:Resolution of myocardial phospholipase C into several forms with distinct properties. 631 25

Rat pancreatic islet homogenates display protein kinase C activity. This phospholipid-dependent and calcium-sensitive enzyme is activated by diacylglycerol or the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In the presence of TPA, the Ka for Ca2+ is close to 5 microM. TPA does not affect phosphoinositide turnover but stimulates [32P]- and [3H]choline-labelling of phosphatidylcholine in intact islets. Exogenous phospholipase C stimulates insulin release, in a sustained and glucose-independent fashion. The secretory response to phospholipase C persists in media deprived of CaCl2. It is proposed that protein kinase C participates in the coupling of stimulus recognition to insulin release evoked by TPA, phospholipase C and, possibly, those secretatogues causing phosphoinositide breakdown in pancreatic islets.
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PMID:Activation of protein kinase C by a tumor-promoting phorbol ester in pancreatic islets. 632 81

In rat jejunal brush-border membranes (BBM), ATP hydrolysis activity was specifically stimulated by CaCl2 and by MgCl2, allowing to identify Ca(2+)-ATPase and Mg(2+)-ATPase activities with a broad pH optimum near 8.0. Nonspecific ATPase activity (in the absence of cations) had a pH optimum above 9.5 as alkaline phosphatase. The effects of Ca2+ and Mg2+ concentrations on ATPase activity evidenced two apparent KA for each cation. At high concentrations, a similar affinity for both cations was recorded (KA: 0.35 mM). At low concentrations, the affinity for Mg2+ was greater than for Ca2+ (KA: 0.02 mM and 0.07 mM respectively). In an attempt to differentially solubilize alkaline phosphatase and ATPase activities, eleven different detergents were assayed. They more or less successfully released Ca(2+)-ATPase and Mg(2+)-ATPase activities from BBM but the more membranes were solubilized by a detergent, the more activities were lost, suggesting a close dependence on integration in BBM. As to alkaline phosphatase and nonspecific ATPase, they almost co-solubilized with Ca(2+)-ATPase and Mg(2+)-ATPase but their total activity was little affected. After treatment of BBM with phosphatidylinositol-specific phospholipase C (E.C. 3.1.4.10), 58% of alkaline phosphatase activity and 45% of nonspecific ATPase activity were released in the supernatant while Ca(2+)-ATPase and Mg(2+)-ATPase activities remained totally incorporated in BBM pellets. These last results definitively demonstrate that Ca(2+)-ATPase and Mg(2+)-ATPase activities are not manifestations of alkaline phosphatase, as earlier suggested, but rather result from the existence of one or several intrinsic membrane enzymes.
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PMID:Ca(2+)-ATPase and Mg(2+)-ATPase activities distinct from alkaline phosphatase in rat jejunal brush-border membranes. 751 33


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