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:3.1.1.8 (cholinesterase)
12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A study in the enzymatic properties of muscle membranes established that sarcolemma of the rabbit skeletal muscles contains the Ca2+-ATPase system which does not require Mg2+ for manifestation of ions activity. By some kinetic properties it differs from ATPase of myosin. The complex Ca-ATP2+ is a substrate of Ca2+-ATPase. Ions of a series of bivalent metals inhibit the latter as well as the passive transport of Ca2+, that may evidence for a definite relation of Ca2+-ATPase with Ca+2 transport in skeletal muscles. Acetyl cholinesterase and AMP-aminohydrolase are strongly bound with the sarcolemma. The sarcolemma structural organization is shown to play a certain role in manifestation of their activity. On the basis of the data obtained when studying the activity in the ATPase systems and dynamics of formation and decay of the intermediate phosphorylated product in the microsomal fraction of cow and rabbit myometrium certain peculiarities are established for the active mechanisms of Ca2+ transport in smooth muscles. A problem is under discussion on the possible active participation of sarcolemma in regulation of Ca2+ concentration in the smooth muscle cells. Two ATPase systems, Mg2+-dependent and Mg2+-dependent Ca2+ activated are found in nuclei; the role of lipids of the skeletal muscles in manifestation of their activity is studied. AMP-amino hydrolase properties are characterized for different areas of the sarcoplasmatic reticulum membranes. The model of E-avitaminous muscular distrophy was used to show disturbances in the structure of sarcolemma and membranes of the sarcoplasmatic reticulum which are accompanied by changes in their ATPase and Ca2+-transporting properties.
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PMID:[Enzymatic properties in muscle membranes]. 12 74

Exposure of rat brain Na+ + K+-ATPase (ATP phosphohydrolase E.C. 3.6.1.3) to concentrations of cassaine greater than 1 x 10(-4) M resulted in a poorly reversible inhibition of this enzyme. Inhibition did not require the presence of ATP and developed rapidly, but the final amount of inhibition observed was independent of time. The amount of inhibition observed at a given concentration of cassaine was reduced by increasing the concentration of membranes in the system. The inhibition of Na+ + K+-ATPase activity was associated with equivalent inhibition of the phosphorylation and (3H)-ouabain binding reactions of this enzyme, while the uninhibited enzyme was apparently kinetically normal. Concentrations of cassaine which produced this stable inhibition of Na+ + K+-ATPase had no effect on the Mg2+-activated ATPase or the NADH cytochrome-c-reductase activities of crude rat brain microsomal preparations. Cassaine inhibited the cholinesterase activity of rat brain microsomes with a Ki of about 5 x 10(-5) M, but his inhibition was fully reversible. The poorly reversible inhibitory actions of cassaine, thus, appeared specific for Na+ + K+-ATPase. Because this stable pattern of inhibition of the Na+ + K+-ATPase by cassaine required drug concentrations at least one hundred-fold greater than those which produce positive inotropic effects, it appears unlikely that this pattern of Na+ + K+-ATPase inhibition is involved in the cardiotonic actions of this drug.
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PMID:Studies on the stable inhibition of Na+ + K+-ATPase by cassaine. 13 Feb 44

A rapid method for purifying Torpedo electric organ vesicles is described, which employs an isoosmotic continuous sucrose-glycine gradient followed by chromagography on CPG-10-3000 porous glass beads. The synaptic vesicles have a buoyant density of 1.057 g/ml. The purified vesicles are free of cholinesterase, lactate dehydrogenase and Na+, K+-stimulated ATPase activity. They contain a ouabaininsensitive, Na+, K+-inhibited, Mg2+, Ca2+-stimulated ATPase activity. This is further stimulated by acetylcholine but not by choline.
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PMID:Adenosine triphosphatase activity associated with purified cholinergic synaptic vesicles of Torpedo marmorata. 14 98

A Cytophaga sp. with the property of liberating a cholinesterase which is found in body muscle of plaice was studied. The liberation was caused by a factor of which more than 90% was found outside the bacterial cell and might possibly be associated within the slime material surrounding the bacteria. Magnesium limitation during growth of Cytophaga sp. in batch cultures resulted in an about 10-fold increase in extracellular factor activity. The increase could be immediately stopped by addition of magnesium ions or chloramphenicol to the medium. The effect of the latter might indicate that the increase in factor activity is dependent on protein synthesis under magnesium-limiting conditions.
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PMID:Increased extracellular production of a cholinesterase-solubilising factor by Cytophaga NCMB 1314 during magnesium starvation. 63 92

1. Rabbit retinas were isolated and superfused with a physiological medium. Ganglion cell activity was recorded during stimulation with focused light, and receptive fields were mapped. Receptive fields were identical to those found in vivo and did not change during a 6-h incubation. After the receptive field of a ganglion cell had been identified, acetylcholine or related agents were introduced singly or in combination into the medium, and their effect on the cell's spontaneous and light-evoked activity was observed. 2. Ganglion cells with on-center or directionally selective receptive fields were excited when ACh was added to the medium. The response to exogenous ACh was prevented by cholinergic antagonists. 3. These cells' spontaneous activity and response to light were enhanced by anticholinesterase and depressed by cholinergic antagonists. Antagonists varied in their ability to block the light-evoked response, with dihydro-beta-erythroidine the most effective. 4. Thresholds for ACh or the related agents were low, ranging from 1 to 40 muM; their effects were rapidly and completely reversed when the retina was returned to control medium. 5. In retinas incubated in medium containing 20 mM Mg2+ and 0.2 mM Ca2+, ganglion cells lost completely both their spontaneous and light-evoked activity, but retained their ability to generate action potentials in response to elevated K+. Ganglion cell activity rapidly returned to normal when the retina was returned to medium containing normal electrolytes. On-center and directionally selective cells were excited by ACh in retinas where synaptic transmission had been inhibited by 20 mM Mg2+ and 0.2 mM Ca2+. 6. The responses of on-center and directionally selective cells to ACh, to anticholinesterase, and to cholinergic antagonists in control medium indicate that the retina contains one or more synapses using ACh as a neurotransmitter. The response to ACh in retinas exposed to 20 mM Mg2+ and 0.2 mM Ca2+ suggests that at least one such synapse in on the ganglion cell itself. 7. Off-center cells were inhomogenous in their response to ACh. Although some responded just as the other classes of cell, the majority responded quite weakly and a subgroup was encountered which was entirely unaffected by even 1 mM ACh, by levels of physostigmine which inactivate virtually all retinal acetyl-cholinesterase, or by high concentrations of cholinergic antagonists. Only 2 of 20 off-cells tested in the presence of 20 mM Mg2+ and 0.2 mM Ca2+ were excited by ACh. Apparently ACh is not a primary transmitter for most off-cells.
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PMID:Responses to acetylcholine of ganglion cells in an isolated mammalian retina. 99 29

Subacute (daily) administration of diisopropylfluorophosphate (DFP) to male swine (Yorkshire white) resulted in a 97% inhibition of cholinesterase and a decrease of [3H]quinuclidinyl benzilate [( 3H]QNB) binding sites in homogenates of striata by approximately 50% after 14 days. The maximal density of receptors (Bmax) decreased from 2.1 +/- 0.3 to 1.0 +/- 0.2 pmole/mg protein. There was no significant change in the dissociation constant (Kd) for [3H]QNB binding (control: 52.6 +/- 10.7 pM; 7-day: 57 +/- 2.8 pM). Carbachol displacement of [3H]QNB binding yielded data best fit by a two-binding site model. The dissociation constants were KiL = 115 +/- 62 microM (55 +/- 3%) and KiH = 1.8 +/- 0.7 microM (45 +/- 3%), respectively, for the low- and high-affinity states. Seven-Day treatment with DFP reduced the percentage of high-affinity receptors to 22 +/- 8.6%, but affected neither the low- nor the high-affinity Kd (100 +/- 20 and 2 +/- 0.6 microM). With the addition of Mg2+, striatal homogenates had low- and high-affinity receptors in the proportion of approximately 1 to 1. In the presence of Gpp(NH)p + Mg2+ the ratio of high- to low-affinity receptors was 3:1 in homogenates of control tissue (to 26 +/- 5%). This treatment had no effect on this ratio in homogenates of tissue from 7-day DFP-treated swine (3:1) since it was already 3:1. Pirenzepine displacement of [3H]QNB binding was best described by a two-binding site model, with Ki values of 38 +/- 14 and 201 +/- 78 nM, which represent 74 and 26% of the binding sites, respectively. The high affinity Kd value was unchanged following 7 days of DFP treatment (24 +/- 5 nM). There appears to be little change in the displacement curves for pirenzepine inhibition of [3H]QNB binding. This suggests that about 75% of the receptors are of the M1 subtype. Thus, subacute administration of DFP causes not only a decrease in the number of receptors, but also a change in the proportion of agonist affinity states which is related to the interaction of the guanine nucleotide binding protein and the muscarinic receptor.
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PMID:Down-regulation of muscarinic receptors in the striatum of organophosphate-treated swine. 238 34

S-mercuric-N-dansylcysteine was investigated as a potential probe of protein sulphydryl groups using bovine serum albumin, S-carboxymethyl-bovine serum albumin, lysozyme, and partially reduced lysozyme as test proteins. Criteria used to assess covalent binding through mercury-bridged mercaptide linkages include a finite reaction time (minutes to hours), abolition of the characteristic fluorescence spectrum following addition of a reducing agent, and failure to separate probe and protein after chromatography or electrophoresis. By these criteria, both Torpedo californica acetylcholinesterase and human serum cholinesterase (butyrylcholinesterase) contain four free sulphydryl groups per tetrameric enzyme molecule whereas Electrophorus electricus acetylcholinesterase has none. Labeled acetylcholinesterase and butyrylcholinesterase remain active and responsive to the inactivator Zn2+. Zn2+ promotes an increase in the fluorescence of bound S-mercuric-N-dansylcysteine, whereas activators such as Mg2+ or gallamine promote a decrease, suggesting that the label may be a useful probe of ligand-induced conformational changes. With T. californica acetylcholinesterase, but not with human serum cholinesterase, Zn2+ also promotes access to two additional groups that are reactive towards the sulphydryl reagent.
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PMID:The reaction of S-mercuric-N-dansylcysteine with acetylcholinesterase and butyrylcholinesterase. 278 87

The properties of a rat liver enzyme that hydrolyzes organophosphorus (OP) inhibitors of cholinesterases were studied. The rates of hydrolysis of OP inhibitors were determined by continuous titration of released hydrogen ions, using a pH stat method. Centrifugation of homogenates at 205,000 g for 30 min demonstrated that the activity was in the soluble fraction. Hydrolysis of sarin, soman, and diisopropyl phosphorofluoridate (DFP), but not of tabun, was stimulated by the addition of Mn2+ and Mg2+. Hydrolysis of sarin greater than soman greater than tabun greater than DFP. Unlike other OP hydrolases that preferentially hydrolyze the non-toxic isomers of soman, this enzyme hydrolyzed all four soman isomers at approximately the same rate. This result was obtained in vitro by gas chromatographic analysis of enzyme-catalyzed soman hydrolysis and confirmed in vivo by demonstrating reduced toxicity in mice of soman partially hydrolyzed by this enzyme. Km and Vmax were determined by fitting V vs [S] to a hyperbolic function using regression analysis. Km values ranged from 1.1 mM for soman to 8.9 mM for tabun. Vmax values ranged from 54 nmol/min/mg protein for DFP to 2694 for sarin. The enzyme was stable for at least 2 months at -90 degrees but was inactivated by heating at 100 degrees for 5 min. Elution profiles from gel filtration by high pressure liquid chromatography showed that the hydrolytic activity for the OP inhibitors eluted in a single peak, suggesting that a single enzyme was responsible for the observed hydrolysis. Further purification and characterization of this enzyme should prove useful for the development of methods for detection, detoxification, and decontamination of these cholinesterase inhibitors.
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PMID:Partial characterization of an enzyme that hydrolyzes sarin, soman, tabun, and diisopropyl phosphorofluoridate (DFP). 291 Mar 6

The active zone is a unique presynaptic membrane specialization that is believed to be the site of neurotransmitter release. To examine directly the relationship between active zone ultrastructure and synaptic efficacy, frog neuromuscular junctions were studied with a new technique combining electrophysiology, light microscopy, and freeze-fracture of identified single muscle fibers. This technique allows correlations to be made between quantal content (measured in low Ca2+ and high Mg2+ Ringer solution), endplate size, and active zone structure at the same neuromuscular junctions. By measuring physiological and morphological variables at the same junctions, the validity of structure-function correlations is significantly improved. Synaptic quantal content in 91 physiologically identified muscle fibers varied considerably and was only poorly correlated with endplate size, as shown in previous studies. To measure the total length of endplate branches, either a modified cholinesterase stain or rhodamine-labeled peanut agglutinin stain was used. When the same identified muscle fibers were freeze-fractured, active zones were exposed in 17 junctions. In a replica that contained a large part of one nerve terminal, there was no detectable gradient in active zone structure along the length of 3 different nerve terminal branches identifiable with both light and electron microscopy. The results from these 17 identified junctions indicate that quantal content per unit terminal length is positively correlated with the amount of active zone per unit terminal length. The estimated total active zone length and total number of active zone particles per junction are also positively correlated with the quantal content in these identified junctions. This study suggests that active zone size and spacing are better indicators of transmitter release than is endplate size and that the active zone may play an important role in regulating synaptic efficacy at the neuromuscular junction.
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PMID:Correlations between active zone ultrastructure and synaptic function studied with freeze-fracture of physiologically identified neuromuscular junctions. 350 Feb 82

The resting efflux of choline from perfused chicken hearts varied from 0.4 to 2.6 nmol/g min, but was constant for at least 80 min in the individual experiments. The rate of choline efflux was found to be equal to the rate of choline formation in the heart, which, from the following reasons, was essentially due to hydrolysis of choline phospholipids. Cardiac content of choline phospholipids (7,200 nmol/g) was much higher than that of acetylcholine (5.5 nmol/g). Resting release of acetylcholine was 0.016 nmol/g min and, after inhibition of cholinesterase, only about 0.1 nmol/g min. Resting efflux of choline was reduced by mepacrine, a phospholipase A2 inhibitor, by perfusion with a Ca2+-free Tyrode's solution containing EGTA and by the combination mepacrine plus Ca2+-free/EGTA solution. In all experiments the reduced choline efflux levelled off within 10 min at about 50%. Omission or elevation of Mg2+ from 1.05 to 10.5 mmol/l had no effect. Resting efflux was increased to 150% by oleic acid (as sodium salt; 2 X 10(-5) mol/l) which is known to activate phospholipase D. Likewise muscarinic agonists (carbachol and acetylcholine) caused facilitation of the efflux of endogenous choline that was blocked by 3 X 10(-7) mol/l atropine. This effect was not reduced, but even slightly enhanced, by mepacrine and by infusion of EGTA in a modified Tyrode's solution (Ca2+-free, 10.5 mmol/l Mg2+). It is concluded that the resting efflux of choline from the heart is essentially due to hydrolysis of choline phospholipids, that half of the efflux is insensitive to mepacrine and is Ca2+-independent (excluding an involvement of phospholipase A2).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of choline efflux from the perfused heart at rest and after muscarine receptor activation. 371 69


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