Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The temperature-dependence of the catalytic activity of acetylcholinesterase (AChE) from rat erythrocyte-ghost membranes and from Torpedo electric-organ membranes was examined. In the case of rat erythrocyte AChE, a non-linear Arrhenius plot was observed both before and after solubilization by a phosphatidylinositol-specific phospholipase C or by proteinase treatment. Similarly, no significant differences were observed in Arrhenius plots of Torpedo electric-organ AChE before or after solubilization. These results support our suggestion that the catalytic subunit of AChE does not penetrate deeply into the lipid bilayer of the plasma membrane and also suggest that care must be taken in ascribing break points in Arrhenius plots of membrane-bound enzymes to changes in their lipid environment.
 ...
PMID:Arrhenius plots of acetylcholinesterase activity in mammalian erythrocytes and in Torpedo electric organ. Effect of solubilization by proteinases and by a phosphatidylinositol-specific phospholipase C. 390 34

Phosphatidylinositol specific phospholipase C from Staphylococcus aureus could solubilize acetylcholinesterase up to 55% from sheep platelets in the presence of ethylenediaminetetra acetic acid (EDTA). The endogenous phosphatidylinositol specific phospholipase C of platelets activated by deoxycholate (at 3-5 mM) could also solubilize the enzyme to a similar extent. The solubilized enzyme could be further purified to apparent homogeneity by affinity chromatography without the use of any detergents. It is suggested that phosphatidylinositol specific phospholipase C will be a useful tool in the solubilization of acetylcholinesterase from mammalian sources and its purification free of detergents. The present study also demonstrates the parallel behaviour of acetylcholinesterase and aryl acylamidase in platelets confirming their identity.
 ...
PMID:The solubilization of platelet membrane-bound acetylcholinesterase and aryl acylamidase by exogenous or endogenous phosphatidylinositol specific phospholipase C. 393 20

Phosphatidylinositol (PI) specific phospholipase C treatment of rabbit platelets caused 95% release of acetylcholinesterase in the supernatant and 4 to 6% hydrolysis of membrane PI in 2 min. Under these conditions there was no cell lysis as monitored by lack of lactate dehydrogenase activity in the medium. The phospholipase C had no activity towards phosphatidylinositol-4- phosphate and phosphatidylinositol-4,5-bis phosphate. Platelets pretreated with the phospholipase C responded normally to thrombin and platelet activating factor. It is concluded that acetylcholinesterase exists in specific interaction with PI in platelet membranes. Further, the membrane protein release phenomenon caused by the PI-specific phospholipase C did not effect the physiological responsiveness of platelets. Possible implications of these findings to the linkage between PI and membrane enzyme are also discussed.
 ...
PMID:Action of phosphatidylinositol specific phospholipase C on platelets: nonlytic release of acetylcholinesterase, effect on thrombin and PAF induced aggregation. 395 30

The hydrophobic, membrane-bound form of Torpedo acetylcholinesterase is specifically solubilized by a phosphatidylinositol-specific phospholipase C, suggesting that acetylcholinesterase is bound to the membrane via a direct and specific interaction with phosphatidylinositol (Futerman et al., Biochem. J. (1985) 226, 369-377). Here we demonstrate the presence of covalently bound inositol in the membrane-anchoring domain of purified Torpedo acetylcholinesterase. Upon removal of this domain, levels of inositol are reduced to only 15-20% of those found in the intact enzyme. The results presented strongly support our suggestion that phosphatidylinositol is indeed involved in anchoring acetylcholinesterase to the plasma membrane.
 ...
PMID:Identification of covalently bound inositol in the hydrophobic membrane-anchoring domain of Torpedo acetylcholinesterase. 400 81

Phosphatidylinositol-specific phospholipase C (PIPLC) quantitatively solubilizes acetylcholinesterase (AChE) from purified synaptic plasma membranes and intact synaptosomes of Torpedo ocellata electric organ. The solubilized AChE migrates as a single peak of sedimentation coefficient 7.0S upon sucrose gradient centrifugation, corresponding to a subunit dimer. The catalytic subunit polypeptide of AChE is the only polypeptide detectably solubilized by PIPLC. This selective removal of AChE does not affect the amount of acetylcholine released from intact synaptosomes upon K+ depolarization. PIPLC also quantitatively solubilizes AChE from the surface of intact bovine and rat erythrocytes, but only partially solubilizes AChE from human and mouse erythrocytes. The AChE released from rat and human erythrocytes by PIPLC migrates as a approximately 7S species on sucrose gradients, corresponding to a catalytic subunit dimer. PIPLC does not solubilize particulate AChE from any of the brain regions examined of four mammalian species. Several other phospholipases tested, including a nonspecific phospholipase C from Clostridium welchii, fail to solubilize AChE from Torpedo synaptic plasma membranes, rat erythrocytes, or rat striatum.
 ...
PMID:Solubilization of membrane-bound acetylcholinesterase by a phosphatidylinositol-specific phospholipase C. 404 59

Binding of acetylcholine in the concentration range 1 nM-1 muM was measured by equilibrium dialysis to a particulate preparation of Torpedo electroplax, without or with prior treatment of the tissue with one of three chemical modifying reagents. Significant reduction in binding of acetylcholine resulted after treatment with 1,4-dithiothreitol, p-chloromercuribenzoate, or p-(trimethylammonium)-benzenediazonium fluoroborate. Partial reversal of the reduction in binding occurred when dialysis was performed in the presence of 5,5'-dithiobis-(2-nitrobenzoic acid) or potassium ferricyanide (in the case of treatment with dithiothreitol), and 2-mercaptoethanol (in the case of treatment with p-chloromercuribenzoate). It is concluded that the functional acetylcholine-receptor macromolecule of Torpedo electroplax has disulfide bond(s), sulfhydryl group(s), and one or more of the amino acids vulnerable to diazotization by p-(trimethylammonium)-benzenediazonium fluoroborate. This, plus the effect of phospholipase C (EC 3.1.4.3) in elimination of detectable binding of acetylcholine after electrofocusing, is additional evidence that the functional acetylcholine receptor is a phospholipoprotein or a phospholipid-protein complex, which has a low isoelectric point of 4.5 +/- 0.2, yet is denatured by exposure to low pH for 24 hr. Due to this adverse effect, recovery of binding of acetylcholine after electrofocusing, as detected by equilibrium dialysis or ultrafiltration, is only 23% and, so far, only 6.3-fold purification of functional acetylcholine receptors by this technique is possible. Three or two forms of acetylcholinesterase (EC 3.1.1.7), whose peaks have isoelectric points ranging from 4.3 to 7.2, appear after electrofocusing of Torpedo extracted with 1% Triton X-100 or Lubrol, respectively. The major peak in either preparation has an isoelectric point of 5. Although the peaks of the functional acetylcholine receptors and of acetylcholinesterase of Torpedo electroplax are separable by electrofocusing, it has not been possible to isolate fractions that contain functional receptors but that are free of acetylcholinesterase. The opposite is possible.
 ...
PMID:Characterization and partial purification of the acetylcholine receptor from Torpedo electroplax. 450 55

The evolution of the cholinergic (nicotinic) receptor in chick muscles is monitored during embryonic development with a tritiated alpha-neurotoxin from Naja nigricollis and compared with the appearance of acetylcholinesterase. The specific activity of these two proteins reaches a maximum around the 12th day of incubation. By contrast, choline acetyltransferase reaches an early maximum of specific activity around the 7th day of development, and later continuously increases until hatching. Injection of alpha-toxin in the yolk sac at early stages of development causes an atrophy of skeletal and extrinsic ocular-muscles and of their innervation. In 16-day embryos treated by the alpha-toxin, the endplates revealed by the Koelle reaction are almost completely absent. The total content and specific activities of acetylcholinesterase and choline acetyltransferase in atrophic muscles are markedly reduced.
 ...
PMID:Effects of a snake alpha-neurotoxin on the development of innervated skeletal muscles in chick embryo. 451 29

Purified alpha-toxin from Naja nigricollis snake venom labeled by [(3)H]acetylation binds specifically to the acetylcholine receptors of mouse neuroblastoma cells. Toxin binding was inhibited by inhibitors for nicotinic and muscarinic acetylcholine receptors. Clones of neuroblastoma cells were selected for low acetylcholinesterase (EC 3.1.1.7) activity with antibodies against this enzyme. Selection for an 80-fold decrease in acetylcholinesterase activity was not associated with any decrease in the number of acetylcholine receptors (3.4 x 10(7) per cell). Removal or inactivation of 80% of the acetylcholine receptors by proteolytic enzymes or by compounds that block sulfhydryl groups did not change the activity of acetylcholinesterase on the cell surface. In addition to these results on the separation between acetylcholine receptors and acetylcholinesterase, a common regulation was found in that both the number of acetylcholine receptors and the activity of acetylcholinesterase were increased 5- to 10-fold when the cells stopped to multiply or were induced to differentiate by dibutyryl-cyclic AMP. It is suggested that there are different genes for the acetylcholine receptor and acetylcholinesterase, and that both are regulated during growth and differentiation by a common regulatory gene.
 ...
PMID:Regulation of acetylcholine receptors in relation to acetylcholinesterase in neuroblastoma cells. 451 44

An equilibrium dialysis technique, applied to lyophilized particulate fractions of Torpedo electroplax, gave data consistent with a single kind of macromolecular binding of muscarone, with binding constant, 7 x 10(-7)M and an amount of 1 nmole per gram original electroplax. The effects on muscarone binding of 38 drugs suggested that muscarone binding reflected acetylcholine receptor activity. Of 18 enzyme preparations, only trypsin, chymotrypsin, and phospholipase C reduced binding activity, suggesting that a phospholipoprotein was binding. Partial "solubilization" of the binding protein was achieved, but the "solubilized" activity did not migrate on electrophoresis. Additional evidence was provided that acetylcholinesterase was not responsible for this muscarone binding.
 ...
PMID:A muscarone-binding material in electroplax and its relation to the acetylcholine receptor. II. Dialysis assay. 526 75

A procedure has been developed for the separation of intrinsic proteins of plasma membranes from the electric organ of Torpedo marmorata. (Na+ + K+)-ATPase, nicotinic acetylcholine receptor and acetylcholinesterase remained active after solubilization with the nonionic detergent dodecyl octaethylene glycol monoether (C12E8). These components could be separated by ion exchange chromatography on DEAE-Sephadex A-25. Fractions enriched in ouabain-sensitive K+-phosphatase or (Na+ + K+)-ATPase activity showed two bands in sodium dodecyl sulphate polyacrylamide gel electrophoresis corresponding to the alpha- and beta-subunits. The (Na+ + K+)-ATPase was shown to have immunological determinants in common with a 93 kDa polypeptide which copurified with the nicotinic acetylcholine receptor, also after solubilization in Triton X-100 and chromatography on Naja naja siamensis alpha-toxin-Sepharose columns. The data suggest that the alpha-subunit of (Na+ + K+)-ATPase associates with the acetylcholine receptor in the membranes of the electric organ.
 ...
PMID:Fractionation of protein components of plasma membranes from the electric organ of Torpedo marmorata. 629 54


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>