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:3.1.1.7 (acetylcholinesterase)
28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Various organophosphorus compounds with low acute toxicity levels are widely used as insecticides. Human acute poisoning by organophosphates has often occurred accidentally. We determined the activity and isoenzyme patterns of serum cholinesterase (ChE) obtained from 13 human patients who attempted suicide with various organophosphates, i.e. Fenitrothion, Malathion, Isoxathion, Pyridaphenthion and Trichlorfon, and studied on the changes in the activity and isoenzyme patterns of serum ChE after ingestion. The following results were obtained. 1) Twenty ChE isoenzyme bands from normal human serum were detected by electrophoretic separation on polyacrylamide gradient gel. The main bands in the ChE isoenzyme pattern in normal serum were bands 4 and 5 which had the highest activity of acetylcholinesterase (AChE) with a molecular weight of 600,000-800,000, and bands 7, 12, 14, 17 and 18. 2) Inhibition of serum ChE activity was more severe as the amount ingested increased in patients who took Fenitrothion and Malathion. Reactivation of serum ChE activity was very slow in patients treated with PAM (2-pyridine aldoxime methiodide) in the late stage of ingestion or whose symptoms reappeared. 3) There were no differences in the patterns of serum ChE isoenzyme by organophosphorus compound. Band 7 disappeared in the serum ChE isoenzyme of almost every patient, and bands 12, 18, 14 and 17 of the serum ChE isoenzyme disappeared successively with the decline of serum ChE activity. Only band 5 of the isoenzyme remained in cases who had serum ChE activity lower than 5% of normal. 4) All 13 patients were treated with PAM and atropine immediately after being admitted to hospitals. We could not clearly determine the efficacy of PAM on reactivation of serum ChE activity and isoenzyme, because it was impossible in human poisoning to compare PAM efficacy with no treatment and with pre- and post-PAM treatment. 5) The activity and isoenzyme patterns of serum ChE recovered rapidly after combined hemoperfusion and hemodialysis treatment (HP-HD treatment) of the patients poisoned with Malathion. But HP-HD treatment had no effect on poisoning by Fenitrothion and Isoxathion. These findings demonstrated the changes in the activity and isoenzyme pattern of serum ChE in patients poisoned with several organophosphates after PAM and HP-HD treatment.
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PMID:[A study on acute organophosphorus poisoning--changes in the activity and isoenzyme patterns of serum cholinesterase in human poisoning]. 810 98

The reaction of human erythrocyte acetylcholinesterase (AChE) with a set of structurally related phosphoramidates was studied in order to investigate the properties of phosphorylated enzyme and the effects of 4 oximes PAM-2, TMB-4, HI-6 and BDB-106 on the reactivation of inhibited AChE. Second-order rate constant of the phosphorylation reaction of the compounds towards the active site of AChE range between 5.0 x 10(2) and 4.9 x 10(6) M-1min-1 and their inhibitory power (I50) was from 7.3 x 10(-5) to 5.7 x 10(-9) M for 20 min incubation at 37 degrees C. The oximes used were weak reactivators of inhibited AChE except for (C4H9O)(NH2)P(O)DCP (DCP, -O-2,5-dichlorphenyl group) and (C6H13O)(NH2)P(O)SCH3 where we have obtained good reactivation. Imidazole oxime BDB-106 proved to be a potent reactivator of tabun-inhibited AChE.
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PMID:Oxime-induced reactivation of acetylcholinesterase inhibited by phosphoramidates. 861 58

The acute toxicity of chlorpyrifos, methylchlorpyrifos, parathion and methylparathion to three age classes of Artemia salina was determined. In general, A. salina 24-h old was less sensitive to these organophosphorous insecticides (OPI) than A. salina 48-h old and A. salina 48-h old was significantly more tolerant than A. salina 72-h old, in contrast, chlorpyrifos was equally toxic to A. salina 48- and 72-h old. There were some differences among the three age classes of A. salina in the relative order of toxicity of OPI tested. The rank order of toxicity to A. salina 48-h old was methylparathion < parathion < methyl-chlorpyrifos < chlorpyrifos, while to A. salina 24- and 72-h old it was methylparathion = parathion < methyl-chlorpyrifos < chlorpyrifos. The protective effect of the cholinergic antagonists atropine, hexamethonium, pirenzepine and 11-(2-((diethyl-amino)methyl)-1-piperidinylacetyl)-5, 11-dihydro-6H-pyrido(2,3-b)-(1,4)-benzodiazepine-6-one (AF-DX 116) and a cholinesterase-reactivating oxime 2-pyridine aldoxime methochloride (2-PAM) on the mortality due to four selected OPI in Artemia salina 24-h old was investigated. The lethal action of OPI tested was completely prevented by pretreatment of Artemia salina 24-h old with 2-PAM (10(-5) M) and atropine (10(-4 )M). However no concentration of hexamethonium, pirenzepine or AF-DX 116 protected 100% of the animals poisoned by LC84 of the OPI selected, maximum protection obtained was 71 to 88%. In contrast, the maximum inhibition of mortality obtained with AF-DX 116 pretreatment was about 55% because this compound was used at concentrations which were non toxic to control Artemia salina. Atropine, hexamethonium, pirenzepine, AF-DX 116 and 2-PAM afforded 50 % protection (IC50) of Artemia salina against mortality by LC84 of the OPI selected at concentrations in the range of 6.62x10(-7)-1.6x10(-6) M, 2. 38x10(-4)-2.05x10(-3)M, 8.91x10(-7)-1.24x10(-6) M, 9.66x10(-8)-1. 34x10(-7 )M, and 1.95x10(-8)-2.73x10(-8 )M, respectively. Pretreatment of atropine plus 2-PAM to determine whether this combination afforded greater inhibition of the lethality induced by four OPI tested than pretreatment with either atropine or 2-PAM alone was investigated. Atropine (10(-5) M) in combination with 2-PAM (10(-7 )M) inhibited completely the acute toxicity of all OPI tested, while the pretreatment with atropine (10(-6) M) plus 2-PAM at the same concentration gave a inhibition of mortality (about 62%) significantly greater than each antagonist alone (about 14 and 46%, respectively).
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PMID:Acute toxicity of several organophosphorous insecticides and protection by cholinergic antagonists and 2-PAM on Artemia salina larvae. 885 33

Reactivators of organophosphate (OP)-inhibited cholinesterases (ChEs) are believed to give rise to phosphorylated oximes (POX) that reinhibit the enzyme. Diethylphosphoryl oximes (DEP-OX) that were generated in situ were demonstrated in the past to be unstable, yet were more potent inhibitors of acetylcholinesterase (AChE) than the parent OPs. In view of the inconsistencies among reported results, and the potential toxicity of POXs, it seemed important to characterize authentic DEP-OXs, and to evaluate their interference with reactivation of diethylphosphoryl-ChE (DEP-ChE) conjugates. To this end, the diethylphosphoric acid esters of 1-methyl-2-pyridinium carboxaldehyde oxime (DEP-2PAM) and 1-methyl-4 pyridinium carboxaldehyde oxime (DEP-4PAM) were synthesized and chemically defined. The half-lives of DEP-2PAM and DEP-4PAM in 10 mM Tris buffer, pH 7.8, at 29 degrees were found to be 10 and 980 sec, respectively. The two DEP-OXs inhibited ChEs with the following ranking order: for DEP-2PAM, human butyrylcholinesterase (HuBChE, k(i) = 2.03 x 10(9) M(-1) min(-1)) > mouse AChE (MoAChE) approximately equal to fetal bovine serum AChE (FBS-AChE) approximately equal to equine BChE (EqBChE); for DEP-4PAM, HuBChE (k(i) = 0.71 x 10(9) M(-1) min(-1)) > EqBChE > MoAChE > FBS-AChE. A dialkylarylphosphate hydrolase (phosphotriesterase; PTE) from Pseudomonas sp. catalyzed the hydrolysis of DEP-4PAM with k(cat)/Km = 3.56 x 10(7) M(-1) min(-1) and Km = 0.78 mM. Reactivation of DEP-ChEs was enhanced by PTE when 4-PAM-based oximes were used as reactivators, whereas reactivation with 2-PAM-based oximes was not affected by PTE. This observation is attributed primarily to the short half-life of DEP-OXs derived from the latter oximes. Relatively low doses of PTE can detoxify large quantities of DEP-OXs rapidly, and thereby augment the efficacy of antidotes that contain the oxime function in position 4 of the pyridine ring.
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PMID:Characterization of O,O-diethylphosphoryl oximes as inhibitors of cholinesterases and substrates of phosphotriesterases. 1042 71

Bovine splenic nerve was used as a source of axolemma-enriched fractions derived from mammalian unmyelinated axons. By electron microscopy, splenic nerve consisted entirely of fascicles of unmyelinated axons and associated Schwann cells. The epineurium and blood vessels were stripped from the dissected nerve, which was then homogenized followed by preparation of a microsomal fraction by differential centrifugation. The microsomes were fractionated on a 10% to 40% continuous sucrose gradient. The individual fractions were combined into six fractions based on sucrose concentration and each fraction was analyzed for membrane markers. The 20% to 23% region of the sucrose gradient was enriched approximately sevenfold in acetylcholinesterase activity and twofold enrichment in saxitoxin binding activity was noted in the same fraction. Relative to other microsomal fractions, this same fraction was less enriched in a microsomal marker (cytochrome c reductase) and only moderately enriched in the activity of a myelin membrane marker (2',3' cyclic nucleotide 3' phosphohydrolase, CNPase). Polyacrylamide electrophoresis of the axolemma-enriched fraction revealed five prominent peptides ranging in molecular weight from 40 kDa to 130 kDa. Lipids, comprising 59.4% of the dry weight, were enriched in cholesterol and sphingomyelin, consistent with the origin from a peripheral nervous system (PNS) plasma membrane. On a molar basis, the major gangliosides were G(T1b), G(D1a), and G(M1). As a whole, these molecular characteristics are consistent with the origin of the axolemma-enriched fraction in the unmyelinated splenic nerve axons. This membrane preparation should prove useful in future studies of the myelinogenic potential of mammalian unmyelinated axolemma.
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PMID:Isolation and characterization of unmyelinated axolemma from bovine splenic nerve. 1046 91

Organophosphates inactivate acetylcholinesterase by reacting covalently with the active center serine. We have examined the reactivation of a series of resolved enantiomeric methylphosphonate conjugates of acetylcholinesterase by two oximes, 2-pralidoxime (2-PAM) and 1-(2'-hydroxyiminomethyl-1'-pyridinium)-3-(4'-carbamoyl-1-pyridinium) (HI-6). The S(p) enantiomers of the methylphosphonate esters are far more reactive in forming the conjugate with the enzyme, and we find that rates of oxime reactivation also show an S(p) versus R(p) preference, suggesting that a similar orientation of the phosphonyl oxygen toward the oxyanion hole is required for both efficient inactivation and reactivation. A comparison of reactivation rates of (S(p))- and (R(p))-cycloheptyl, 3,3-dimethylbutyl, and isopropyl methylphosphonyl conjugates shows that steric hindrance by the alkoxy group precludes facile access of the oxime to the tetrahedral phosphorus. To facilitate access, we substituted smaller side chains in the acyl pocket of the active center and find that the Phe295Leu substitution enhances the HI-6-elicited reactivation rates of the S(p) conjugates up to 14-fold, whereas the Phe297Ile substitution preferentially enhances 2-PAM reactivation by as much as 125-fold. The fractional enhancement of reactivation achieved by these mutations of the acyl pocket is greatest for the conjugated phosphonates of the largest steric bulk. By contrast, little enhancement of the reactivation rate is seen with these mutants for the R(p) conjugates, where limitations on oxime access to the phosphonate and suboptimal positioning of the phosphonyl oxygen in the oxyanion hole may both slow reactivation. These findings suggest that impaction of the conjugated organophosphate within the constraints of the active center gorge is a major factor in influencing oxime access and reactivation rates. Moreover, the individual oximes differ in attacking orientation, leading to the presumed pentavalent transition state. Hence, their efficacies as reactivating agents depend on the steric bulk of the intervening groups surrounding the tetrahedral phosphorus.
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PMID:Mechanism of oxime reactivation of acetylcholinesterase analyzed by chirality and mutagenesis. 1080 25

In vitro study for the determination of the toxicity of some pesticides (glyphospate and paraquat) and cadmium chloride (CdCl2) on the activities of serum acetylcholinesterase (AChE), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AlP), and acid phosphatase (AcP) is described. Changes in electrophoretic patterns of serum proteins were also tested. Results revealed that glyphosate was effective on all enzymes except AcP. Its IC50 values (the concentration of compound that inhibits 50% of the enzyme activity in 1 h at 37 degrees C) were 714.3, 750, 54.2, 270.8, and 71.4 mM for AChE, LDH, AST, ALT, and AlP, respectively. The inhibitory effect of paraquat varied markedly among all enzymes. The IC50 values of paraquat were 321.4 and 750 mM for AST and ALT, respectively. It had mild effect on AChE and LDH; and no effect on the activities of AlP and AcP. The effect of CdCl2 was pronounced with AChE, ALT, AlP, and AcP, and no effect on LDH and AST was found. The corresponding IC50 values were 77.7, 22.2, 33.3, and 83.3 mM for AChE, ALT, AlP, and AcP, respectively. Polyacrylamide gel electrophoretic patterns of serum proteins showed marked differences with glyphosate and CdCl2 but not with paraquat. The results suggest that the in vitro enzyme-activity test seems to have a potential for the assessment of pesticide and heavy metal toxicity.
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PMID:Influence of paraquat, glyphosate, and cadmium on the activity of some serum enzymes and protein electrophoretic behavior (in vitro). 1128 Dec 53

The acute toxicity of carbophenothion to three age classes of Artemia salina was evaluated. An increase in toxicity of carbophenothion was found following longer development of A. salina. The effect of pretreatment with the nonselective muscarinic antagonist atropine, the two reversible acetylcholinesterase-inhibitors physostigmine and pyridostigmine, and the cholinesterase-reactivating oxime 2-pyridine aldoxime methochloride (2-PAM) on carbophenothion-induced lethality in 24-h-old A. salina was also investigated. The lethal action of carbophenothion was completely prevented by pretreatment of A. salina with 2-PAM. Atropine and pyridostigmine afforded a maximal protection of approximately 87% and 72%, respectively, compared to control values. In contrast, physostigmine was ineffective. The inhibitory effects of combinations of 10(-5) M atropine with physostigmine, pyridostigmine, or 2-PAM were greater than those elicited by either drug alone, with the maximum protection afforded being 92.58%, 100%, and 100%, respectively. In the presence of 10(-7) M atropine, neither pyridostigmine nor 2-PAM provided additional inhibition of the lethality compared to that with either drug alone, whereas the protection afforded by 10(-7) M atropine plus physostigmine increased as the concentration of carbamate increased (up to 10(-3) M). Pretreatment with pyridostigmine or physostigmine plus 2-PAM (10(-6) M) slightly enhanced the maximal inhibition of carbophenothion lethality compared to that with either drug alone. It is suggested that the most active combined pretreatment studied here was physostigmine plus atropine.
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PMID:The use of carbamates, atropine, and 2-pyridine aldoxime methoiodide in the protection of Artemia salina against poisoning by carbophenothion. 1152 28

The purification of a soluble acetylcholinesterase from Japanese quail brain using affinity chromatography on concanavalin A-Sepharose and edrophonium-Sepharose is described. The affinity matrix was synthesized by coupling an inhibitor edrophonium to epoxy-activated Sepharose. Acetylcholinesterase was purified 10,416-fold with a specific activity of 2500 U/mg protein. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol gave only one band with a molecular weight of 62.5 kDa. The molecular weight of the purified acetylcholinesterase was estimated to be 245.5 kDa by gel chromatography on Sephacryl S-200 under nondenaturing conditions. Based on the molecular weight obtained by both SDS-PAGE and gel filtration the purified acetylcholinesterase was assumed to be a tetrameric form.
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PMID:Purification of soluble acetylcholinesterase from Japanese quail brain by affinity chromatography. 1180 23

Insecticide bioassays were carried out on larvae and adults of rosy eye mutant and wildtype strains of A. aegypti. Both the strains were equally susceptible to DDT, malathion and deltamethrin. Biochemical assays showed an increase in acetylcholinesterase enzyme (AChE) activity in all the stages of mutant strain with both the substrates i.e. acetylthiocholine iodide and S-butyrylthiocholine iodide. However, there was no difference in the percent inhibition of enzyme activity with propoxur in these two strains. Polyacrylamide gel electrophoresis performed in native conditions on the homogenates of adults of rosy eye mosquitoes showed that AChE-II allele was highly active with the substrate acetylthiocholine iodide as compared to wildtype strain. Frequency of the highly active AChE-II allele in the mutant strain was about 68%, whereas it was about 5% in the wildtype strain.
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PMID:Highly-substrate active isoenzyme acetylcholinesterase-II, in rosy eye mutant of Aedes aegypti mosquito. 1201 85


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