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)

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

Sarcolemmal Ca++-ATPase, Mg++-ATPase, and (Na+-K+)-ATPase activities were increased in late stages of heart failure in myopathic hamsters (BIO 14.6) without any changes in the adenylate cyclase activity. On the other hand, these hamsters at early and moderate stages of heart failure showed depressions in mitochondrial calcium binding and uptake and microsomal calcium binding. Sarcolemmal (Na+-K+)-ATPase was decreased in failing hearts because of substrate lack, oxygen lack, and perfusion with Ca++-free, Na+-free, or K+-free medium. Both Mg++-ATPase and Ca++-ATPase activities of sarcolemma did not change on perfusing the hearts with substrate-free, hypoxic, Na+-free, or K+-free medium. Adenylate cyclase activity decreased on substrate-free or Ca++-free perfusion. Intracellular calcium overload produced by perfusing the hearts with medium containing calcium after Ca++-free perfusion was associated with decrease in all the sarcolemmal-bound enzyme activities. All types of failing hearts employed in this study showed a dramatic shift in the electrolyte composition. Failure of the cardiac muscle to generate contractile force on treatment with trypsin was associated with defects in the functions of sarcolemma, mitochondria, and sarcoplasmic reticulum, whereas such an effect on treatment with phospholipase C was limited to alterations in the activities of sarcolemma. The data suggest that abnormality at the level of sarcolemma plays an important role in the pathogenesis of heart dysfunction; however, the degree and direction of alterations in the sarcolemmal functions seem to be dependent upon the type of heart failure.
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PMID:Role of sarcolemmal changes in cardiac pathophysiology. 13 Jun 63

A preparation enriched in junctional complexes, as judged by marker enzymes and electron microscopy, was prepared from rat cerebellum. The junctional complexes were incubated with gamma-amino [14C]butyric acid at 25degreesC for 10 min, using [3H]sucrose as a marker for entrapped space, Total binding was determined in the absence of, and non-specific binding in the presence of, and excess of unlabelled gamma-aminobutyric acid. The difference bewteen the two binding values, i.e. the specific binding, was saturable and reversible, and showed positive cooperativity with a Hill number of about 2. The specific binding was inhibited by N-methylbicuculline, picrotoxinine and imidazole-4-acetic acid, but not by curare, strychnine or L-2,4-diaminobutyric acid. The above compounds had little effect on the non-specipic binding, but addition of ethylenediaminetetraacetic acid decreased non-specific binding by 80%. Trypsin, pronase, phospholipase A2 (EC 3.1.1.4), lysolecithin and sodium dodecyl sulfate decreased binding. Phospholipase C (EC 3.1.4.3) increased the specific binding by 260%. Phospholipids competed with gamma-aminobutyric acid for binding, with phosphatidylethanolamine being more potent than phosphatidylcholine. These results lend support for Watkins' hypothesis that phosphatidylethanolamine competes with gamma-aminobutyric acid for binding to the receptor protein.
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PMID:The effect of phospholipases and proteases on the binding of gamma-aminobutyric acid to junctional complexes of rat cerebellum. 13 18

Treatment of red cell membranes with pure phospholipase C inactivates (Na+ + K+)-ATPase activity and Na+-dependent phosphorylation but increases K+-dependent phosphatase activity. When phospholipase A2 replaces phospholipase C, all activities are lost. Activation of K+-dependent phosphatase by treatment with phospholipase C is caused by an increase in the maximum rate of hydrolysis of p-nitrophenylphosphate and in the maximum activating effect of K+, the apparent affinities for substrate and cofactors being little affected. After phospholipase C treatment K+-dependent phosphatase is no longer sensitive to ouabain but becomes more sensitive to N-ethylmaleimide. In treated membranes Na+ partially replaces K+ as an activator of the phosphatase. Although ATP still inhibits phosphatase activity, neither ATP, nor ATP+Na+ are able to modify the apparent affinity for K+ of K+-dependent phosphatase in these membranes.
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PMID:ATPase and phosphatase activities from human red cell membranes. III. Stimulation of K+-activated phosphatase by phospholipase C. 14 59

1. The requirement for specific polar head groups of phospholipids for activity of purified (Na+ + K+)ATPase from rabbit kidney outer medulla has been investigated. 2. Comparison of content and composition of phospholipids in microsomes and the purified enzyme indicates that purification leads to an increase in the phospholipid/protein ratio and in phosphatidylserine content. 3. The purified preparation contains 267 molecules phospholipid per molecule (Na+ + K+)-ATPase, viz. 95 phosphatidylcholine, 74 phosphatidylethanolamine, 48 spingomyelin, 35 phosphatidylserine and 15 phosphatidylinositol. 4. Complete conversion of phosphatidylserine into phosphatidylethanolamine by the enzyme phosphatidylserine decarboxylase has no effect on the (Na+ + K+)-ATPase activity of the purified preparation. 5. Complete hydrolysis of phosphatidylinositol by a phospholipase C from Staphylococcus aureus, which is specific for this phospholipid, has no effect on the (Na+ + K+)-ATPase activity. 6. Hydrolysis of 95% of the phosphatidylcholine and 60--70% of the spingomyelin and phosphatidylethanolamine by another phospholipase C (Clostridium welchii) lowers the (Na+ + K+)-ATPase activity by about 20%. 7. Combination of the phospholipid-converting enzymes has the same effect as can be calculated from the effects of the enzymes separately. Only complete conversion of both phosphatidylserine and phosphatidylinositol results in a loss of 44% of the (NA+ + K+)-ATPase activity and 36% of the potassium 4-nitrophenylphosphatase activity. 8. These experiments indicate that there is no absolute requirement for one of the polar head groups, although in the absence of negative charges the activity is lower than in their presence.
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PMID:Role of negatively charged phospholipids in highly purified (Na+ + K+)-ATPase from rabbit kidney outer medulla studies on (Na+ + K+)-activated ATPase, XXXIX. 14 6

Incubation of rabbit kidney microsomes with pig pancreatic phospholipase A2 produced residual membrane preparations with very low (Na+ + K+)-ATPase activity. The activity could be restored by recombination with lipid vesicles of negatively-charged glycerophospholipids. Vesicles of pure phosphatidylcholine and phosphatidylethanolamine were virtually inactive in this respect, but could reactivate in the presence of cholate. Incubation of the microsomes with a combination of phospholipase C (Bacillus cereus) and spingomyelinase C (Staphylococcus aureus) resulted in 90--95% release of the phospholipids. The residual membrane contained only phosphatidylinositol and still showed 50--100% of the (Na+ + K+)-ATPase activity.
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PMID:Phosphatidylinositol as the endogenous activator of the (Na+ + K+)-ATPase in microsomes of rabbit kidney. 14 7

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 gonadotropin receptors associated with plasma membrane fractions were solubilized by detergents, including Triton X-100, Lubrol WX, Lubrol PX and sodium deoxycholate before and after equilibration with 125I-labelled human chorionic gonadotropin. The binding activity remained in solution even after centrifugation at 300 000 X g for 3 h. The solubilized gonadotropin receptor or gonadotropin receptor complex was characterized by gel filtration and sucrose density gradient centrifugation. Sucrose density gradient centrifugation of solubilized gonadotropin-receptor complex in the presence of Triton X-100 had a sedimentation coefficient of 6.5 S whereas the solubilized uncomplexed receptor had a sedimentation coefficient of 5.1 S. In the absence of the detergent, solubilized hormone receptor complex from plasma membrane fractions I and II sedimented with an apparent sedimentation coefficient of 6.6 S and 7.4 S, respectively. Similarly, the free receptor also showed higher sedimentation profile with an apparent sedimentation coefficient of 6.7 S for fraction I and 7.2 S for fraction II. Treatment of plasma membranes with phospholipase A and C inhibited the binding of 125I-labelled human chorionic gonadotropin in a dose dependent manner, whereas phospholipase D was without any effect. Doses of 1.4 mI. U. of phospholipase A or 0.6 mI.U. of phospholipase C were required to produce 50% inhibition of the binding activity. These phospholipases had no effect on the preformed 125I-labelled human chorionic gonadotropin-receptor complex nor on the sedimentation profile of solubilized gonadotropin receptor complex.
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PMID:Sedimentation behavior of solubilized gonadotropin receptor from plasma membranes of bovine corpus luteum. 17 61

1. Phospholipase C[EC 3.1.4.3] was purified from the culture filtrate of Clostridium perfringens by successive chromatographies on CM-Sephadex, DEAE-Sephadex, and Sephadex G-100. During the purification it was noted that, beside the monomer form of the enzyme which was purified, a part of the enzyme existed in active polymerized forms. 2. The purified preparation gave a single band on polyacrylamide gel electrophoresis and gave a single precipitin line in immunodiffusion with the National Standard gas gangrene (C. perfringens) antitoxin, indicating the homogeneity of the preparation. 3. The specific lecithin-hydrolyzing activity of the purified preparation was comparable to that of a preparation obtained by affinity chromatography, which had the highest specific activity previously reported. 4. The molecular weight of the purified enzyme was estimated to be 43,000 by SDS-polyacryl-amide gel electrophoresis, although the same preparation gave a molecular weight of 31,000 as determined by gel filtration on Sephadex G-150. From this and the above finding that a part of the enzyme exists in active polymerized forms, the discrepancy among reported values for the molecular weight of C. perfringens phospholipase C can be accounted for. 5. For maximum hydrolytic activity toward lecithin, the enzyme required sodium deoxycholate (SDC) and Ca2+ ions. In the presence of 6 mM Ca2+, the optimal molar ratio of SDC to lecithin for maximal hydrolytic activity was about 0.5 for dipalmitoyl lecithin and about 1.0 for egg lecithin. The effects of various divalent cations on the enzymatic hydrolysis were also investigated. 6. The effects of sodium deoxycholate and Ca2+ ions on the enzymatic hydrolysis are discussed, based on their possible roles in mixed micelle formation.
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PMID:Purification and some properties of phospholipase C (alpha-toxin) of Clostridium perfringens. 19 35

The phospholipid depletion of rat liver mitochondria, induced by acetoneextraction or by digestion with phospholipase A2 or phospholipase C, greatly inhibited the activity of NADH-cytochrome c reductase (rotenone-insensitive). A great decrease of the reductase activity also occurred in isolated outer mitochondrial membranes after incubation with phospholipase A2. The enzyme activity was almost completely restored by the addition of a mixture of mitochondrial phospholipids to either lipid-deficient mitochondria, or lipid-deficient outer membranes. The individual phospholipids present in the outer mitochondrial membrane induced little or no stimulation of the reductase activity. Egg phosphatidylcholine was the most active phospholipid, but dipalmitoyl phosphatidylcholine was almost ineffective. The lipid depletion of mitochondria resulted in the disappearance of the non-linear Arrhenius plot which characterized the native reductase activity. A non-linear plot almost identical to that of the native enzyme was shown by the enzyme reconstituted with mitochondrial phospholipids. Triton X-100, Tween 80 or sodium deoxycholate induced only a small activation of NADH-cytochrome c reductase (rotenone-insensitive) in lipid-deficient mitochondria. The addition of cholesterol to extracted mitochondrial phospholipids at a 1 : 1 molar ratio inhibited the reactivation of NADH-cytochrome c reductase (rotenone-insensitive) but not the binding of phospholipids to lipid-deficient mitochondria or lipid-deficient outer membranes. These results show that NADH-cytochrome c reductase (rotenone-insensitive) of the outer mitochondrial membrane requires phospholipids for its activity. A mixture of phospholipids accomplishes this requirement better than individual phospholipids or detergents. It also seems that the membrane fluidity may influence the reductase activity.
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PMID:The role of lipid-protein interactions in NADH-cytochrome c reductase (rotenone-insensitive) of rat liver mitochondria. 21 8


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