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)

1. Guanylate cyclase of washed particles and plasma membranes showed S-shaped progress curves when titrated with either GTP or Mn2+ ions; similar results were obtained with Triton X-100-solubilized enzyme preparation from washed particles. Hill plots of these data revealed multiple metal-nucleotide and free-metal binding sites. 2. Guanylate cyclase of supernatant fractions displayed typical Michaelis-Menten properties when enzyme required excess of (free) Mn2+ (over GTP) for maximal activities; Ka (free Mn2+) was about 0.15-0.25 mM at subsaturating concentrations of GTP. 4 MnATP, MnADP, and MnGDP were found to increase the activities of both particulate and superantant enzyme, when MnGTP concentration was below saturation and free Mn2+ ion concentration was low (less than 100 muM); MnATP (50muM-1 mM) inhibited both these activities at high free Mn2+ concentration (1.5 mM) and inhibition of the particulate enzyme was greater than that of supernatant enzyme. 5. Ca2+ ions stimulated supernatant-enzyme activity; the stimulatory concentration of Ca2+ ions depended on the concentration of Mn2+ and GTP. 6. A modest stimulation of particulate guanylate cyclase by pyrophosphate (0.02-1 mM) was observed; the pyrophosphate effect appeared to be competitive with respect to GTP. At a higher concentration (2 mM), pyrophosphate produced a marked inhibition of particulate enzyme; the nature of inhibitory effect appeared complex. 7. Inorganic salts (e.g. NaCl, KCl, LiBr, NaF) produced inhibition of particulate enzyme; the degree of inhibition of Triton X-100-stimulated activity was less than that of unstimulated activity. 9. Treatment of sarcolemmal or microsomal membranes with either phospholipase C or trypsin decreased, whereas phospholipase A increased, the activity of guanylate cyclase.
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PMID:Properties of particulate, membrane-associated and soluble guanylate cyclase from cardiac muscle, skeletal muscle, cerebral cortex and liver. 1 Aug 91

Intact microsomes isolated from rat liver showed no hexose-6-phosphate dehydrogenase activity, but the enzyme was activated by Triton X-100, deoxycholate, NH4OH, glycine/NaOH, lysophosphatidylcholine, phospholipases A and C, pancreatic lipase and cholesterol esterase, and also by sonic treatment. The enzyme activation by deoxycholate, NH4OH and sonic treatments was solely due to solubilization, while that by phospholipase A appeared to be due to the detergent action of the hydrolysis products. On the other hand, the primary effects of phospholipase C, cholesterol esterase and pancreatic lipase might be accounted for by the partial removal of membrane lipids. The results of washing and trypsin digestion experiments suggested that hexose-6-phosphate dehydrogenase is one of the most firmly bound enzymes among the microsomal proteins. The catalytic properties were the same in the solubilized and the membrane-bound, activated enzymes. Feeding the rats on a high carbohydrate diet altered the extent of enzyme activation by sonication and phospholipase C treatment, suggesting that the microsomal membrane would actually undergo changes in the conformation and/or chemical composition under certain circumstances.
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PMID:Latency of microsomal hexose-6-phosphate dehydrogenase activity. 1 59

The effects of a variety of agents on guanylate cyclase activity were tested in broken cell preparations of mammary glands from midpregnant mice. Of the agents tested, only phospholipase A, triton X-100, and an impure egg lysolecithin preparation enhanced the activity of guanylate cyclase in mammary gland homogenates; other agents, including sodium azide and phospholipase C, and purified egg lysolecithin had no effect. Phospholipase A increased the activity of guanylate cyclase in the 150,000 g pellet fractions of mammary gland homogenates, bud did not consistently enhance guanylate cyclase in the 150,000 g supernatant fractions. Phospholipase A did not appear to enhance guanylate cyclase activity by solublizing the enzyme from the 150,000 g pellet. Triton X-100, in contrast, appeared to act by solubilizing guanylate cyclase from the material present in the 150,000 g pellet. Triton X-100 increased by several fold guanylate cyclase activity in the tissue homogenates and the 150,000 g pellets, but did not consistently enhance enzyme activity in the 150,000 g supernatant. Triton X-100 had no effect on the apparent Km of guanylate cyclase.
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PMID:Effects of phospholipase A and triton x-100 on guanylate cyclase activity in mammary gland homogenates from mice. 2 72

1-Amino-4-octylpiperazine, AP 22, an antiviral agent causes lipid accumulation in nervous tissue cultures. A physicochemical membrane model was used to demonstrate the formation of a lipid-AP 22 complex hindering phospholipase A2 action. A well defined amphiphilic balance seems essential to explain the mode of action of the drug. The hydrophilic group prevents enzyme-substrate complex formation whereas the hydrophobic group allows the penetration in the lipid layer and determines the stability of the drug-lipid complex. This stability of the drug-lipid association has a direct influence on phospholipase A2 activity but does not affect phospholipase C activity. No inactivation of phospholipase A2 due to a drug-enzyme interaction could be detected.
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PMID:Phospholipase inactivation induced by an amino-piperazine derivative: a study at the lipid-water interface. 3 Aug 13

The role of phospholipids in the binding of [3H]tetrodotoxin to garfish olfactory nerve axon plasma membrane was studied by the use of purified phospholipases. Treatment of the membranes with low concentrations of either phospholipase A2 (Crotalus adamanteus and Naja naja) or phospholipase C (Bacillus cereus and Clostridium perfringens) resulted in a marked reduction in tetrodotoxin binding activity. A 90% reduction in the activity occurred with about 45% hydrolysis of membrane phospholipids by phospholipase A2, and with phospholipase C the lipid hydrolysis was about 60--70% for a 70--80% reduction in the binding activity. Phospholipase C from B. cereus and Cl. perfringens had similar inhibitory effects. Bovine serum albumin protected the tetrodotoxin binding activity of the membrane from the inhibitory effect of phospholipase A2 but not from that of phospholipase C. In the presence of albumin about 25% of the membrane phospholipids remained unhydrolyzed by phospholipase A2. It is suggested that these unhydrolyzed phospholipids are in a physical state different from the rest of the membrane phospholipids and that these include the phospholipids which are directly related to the tetrodotoxin binding component. It is concluded that phospholipids form an integral part of the tetrodotoxin binding component of the axon membrane and that the phospholipase-caused inhibition of the binding activity is due to effects resulting from alteration of the phospholipid components.
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PMID:Effect of purified phospholipases on the binding of tetrodotoxin to axon plasma membrane. 3 72

The physicochemical structure of the receptor for antibody (FcR) on B cells and its interrelationship with Ig and H-2 gene complex associated antigens were examined. FcR were found to be sensitive to treatment with phospholipase C and pronase, but resistant to neuraminidase, phospholipase A and chymotrypsin. They would therefore appear to be composed of phospholipoproteins. Several lines of evidence indicated that FcR and Ig receptors were discrete entities: thus, FcR (1) were resistant to chymotrypsin; (2) capped independently of Ig, as demonstrated by means of Fab fragments of anti-Ig, and (3) were closely associated with at least some Ia determinants, which are known to be distinct from Ig determinants. The relationship between FcR and H-2 gene complex associated antigens was confirmed by demonstrating inhibition of binding of aggregates by anti-Ia serum and vice versa. If, however, FcR were capped, anti-Ia serum applied under non-capping conditions was still found to bind diffusely to the great majority of B cells. Although this could be explained in part by the presence of residual FcR, some Ia determinants appeared to be distinct from FcR. The finding of residual FcR after capping with aggregates or immune complexes implied that FcR are a more integral part of the cell membrane than Ig receptors and could therefore act as proreceptors for the latter. Consistent with this was the demonstration of a significant polar distribution of Ig on B cells capped for FcR and then labelled under non-capping conditions with anti-Ig.
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PMID:A receptor for antibody on B lymphocytes. III. Relationship to immunoglobulin and ia determinants. 5 90

1. The accessibility of phospholipids in the membrane of the adrenomedullary storage vesicles (chromaffin granules) has been studied. 2. The reaction of 2,4,6-trinitrobenzenesulphonic acid with both intact granules and their ghosts, results in the labelling of 70% of the phosphatidylethanolamine. 3. The action of phospholipase A2 (from bee venom), phospholipase C (from Bacillus cereus) and sphingomyelinase C (from Staphylococcus aureus) on granules and their ghosts was followed as a function of time. No significant difference was observed between the intact granules and their ghosts. 4. In the intact granules the various treatments led to varying amounts of lysis although again no evidence was obtained that such lysis in any way increased the amount of accessible phospholipid. 5. Highly purified granule preparations were also compared with the so-called "large granule" fraction and no significant differences were detected. 6. Approx. 67% of phosphatidylethanolamine + phosphatidic acid, 50% of phosphatidylserine + phosphatidylinositol, 65% of phosphatidylcholine and 20% of sphingomyelin is accessible to enzymatic degradation. In total, approx. 50% of all the phospholipids reacted. 7. It is also shown that, unlike in enzymatic treatment, all the phosphatidylcholine can be exchanged in the presence of a phospholipid exchange protein (prepared from beef liver). 8. It is concluded that transmembrane movement of phosphatidylcholine is slow in isolated membranes of chromaffin granules. The presence of the exchange protein, however, in conjunction with membrane proteins and specific phospholipid arrangements may catalyse this transmembrane movement.
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PMID:Accessibility of phospholipids in the chromaffin granule membrane. 10 48

The Rho(D) antigen of red cell membranes was solubilized using ethylene-diamine tetraacetic acid (EDTA) and 2-mercaptoethanol. The solubilized antigen was partially separated from other solubilized membrane components using molecular filtration. The antigen was treated with various enzymes to learn some of the chemical characteristics. It was found that the activity of the antigen, as measured by hemagglutination inhibition, was not affected by bee venom phospholipase A, Clostridium welchii phospholipase C, calf-intestinal alkaline phosphatase, Vibrio cholerae neuraminidase, pig kidney leucine aminopeptidase, bovine pancreatic carboxypeptidase A, and pig pancreatic carboxypeptidase B. However, the proteolytic enzymes, pronase, trypsin, chymotrypsin and papain, did destroy Rho(D) activity as measured by hemagglutination inhibition. These results indicate that protein is an important part of the active determinant of the Rho(D) antigen. The experiments by other investigators have shown that lipid is important to maintain the Rho(D) activity in the intact membrane; lipid probably helps to maintain the structural conformation of the Rho(D) molecule in its natural environment. The solubilized Rho(D) molecules are apparently not dependent on lipid for their Rho(D) activity.
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PMID:Studies on the characterization of the Rho(D) antigen. 10 79

Incubation of Rh positive ghosts with phospholipase A2 and C abolished the adsorption of Rh antibodies on the ghosts; incubation with phospholipase D, however, did not affect their adsorption and none of these phospholipases affected the adsorption of antibodies of the ABO system. The impairment of antigen-antibody-reaction in Rh positive ghosts treated with phospholipase corresponds to the absence of the antigen-antibody reaction with the membrane protein associated with Rh characteristics in the Schultz-Dale-Test. The chromatogram of the phospholipids extracted from those stromata treated with various phospholipases and those not treated showed different patterns. After incubation with phospholipase-A2 the lecithin and cephalin streaks were reduced and in addition lysophosphatide and fatty acid streaks were detected. In the case of phospholipase C the lecithin and cephalin streaks were further reduced while diglyceride streaks made their appearance. The phospholipid extracts from those stromata treated with phospholipase D and those not treated were identical. Phospholipase C reduced the values of lipid phosphorus more than did phospholipase A2, while phospholipase D did not reduce them at all. This study supports the results of other investigators who have postulated that the Rh antigens are located in a lipoprotein on the membrane of the human erythrocyte. The antigen-antibody-reaction seems to require a precise protein-phospholipid interaction.
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PMID:[The importance of phosphatidylcholine in the binding of anti-D to human erythrocyte ghost membrane (author's transl)]. 12 77

The Km value for the dog heart (Na+-K+)-ATPase was 0.31 mM (MgATP), whereas the values for the concentrations of K+ and Na+ varied from 1.2 to 2.7 mM and 12 to 20 mM for half-maximal activation, respectively. The concentrations of ouabain and calcium for 50 percent inhibition of (Na+-K+)-ATPase activity varied from 2.4 to 3.2 muM and 0.5 to 1.2 mM, respectively, the inhibitory effects of these agents were pH dependent. This preparation bound about 50 nmoles of 1-anilino-8-napthaline sulfonate (ANS)/mg of protein and exhibited fluorescence attributable to the ANS-enzyme complex. Cations such as Na+,K+,Ca++, and Mg++ increased ANS-enzyme fluorescence intensity and the number of ANS binding sites but decreased the apparent ANS binding constant. The enzyme activity, ANS binding, and ANS-enzyme fluorescence were decreased by phospholipase A, phospholipase C, and trypsin treatments. Although ouabain inhibited enzyme activity and ANS-enzyme fluorescence markedly, it caused only a slight depression in ANS binding. These results extend support for the allosteric nature of the cardiac (Na+-K+)-ATPase and provide evidence for conformational changes during its activation by Na+ and K+.
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PMID:Characterization of partially purified heart sarcolemmal Na+-K+-stimulated ATPase. 13 Jun 58


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