Hydrolysis Of Acetylcholine Research Articles

Macrocyclic derivatives of 6-methyluracil: New ligands of the peripheral anionic site of acetylcholinesterase.

Acetylcholinesterase (AChE) inhibitors are widely used in medicine for pharmacological correction of cholinergic neurotransmission pathologies such as myasthenia gravis (MG) and Alzheimer's disease [1, 2]. The efficacy of anti-AChE drugs is based on their ability to potentiate the effects of acetylcholine (ACh) due to a decrease in the rate of AChE-catalyzed hydrolysis of ACh. Crystallographic studies showed that the active site of AChE is located at the bottom of a deep gorge [3]. It was shown that, in addition to its catalytic center, AChE has other sites that are crucial for the proper functioning of the enzyme. In particular, the so-called peripheral anionic site (PAS) located at the entrance of the active site gorge is responsible for: 1) allosteric modulation of the catalytic center; 2) enzyme inhibition at high substrate concentration; 3) and non-catalytic functions such as enhancement of cell adhesion and neurite outgrowth. Especially interesting is the relationship between the PAS and pathological beta-amyloid deposition. This led to a new hypothesis for rational design of more effective anti-Alzheimer drugs [4]. Concentration of drug producing 50% of AChE activity inhibition (IC50) was measured using the method of Ellman et al. [5]. Toxicological experiments were performed using IP injection of the different compounds in mice. LD50, dose (in mg/kg) causing lethal effects in 50% of animals was taken as a criterion of toxicity [6]. Molecular docking was performed with Autodock 4.2.6 software. We described previously a new class of selective mammalian AChE vs. butyrylcholinesterase (BChE) inhibitors based on alkylammonium derivatives of 6-methyluracil of acyclic topology [7]. In the present study, taking acyclic derivatives of 6-methyluracil as a model AChE inhibitor, we attempted to develop AChE inhibitors that specifically bind to the PAS with weak binding to the active site of AChE. We attempted to increase the size of AChE ligands to restrict specific binding to the PAS of AChE. To this aim we synthesized pyrimidinophanes bearing two o-nitrobenzylethyldialkylammonium heads. Almost all of synthesized pyrimidinophanes inhibited AChE in the nanomolar range. Based on molecular docking simulations, it was suggested that compounds bind AChE to the active center as well as to the PAS or only to the PAS. Thus, we found that introduction of the spacer, flexible or rigid, between [5-(o-nitrobenzylethylammonium)pentyl] units at N atoms of the 6-methyluracil moiety allows tuning the binding of 6-methyluracil derivatives with AChE. In conclusion, it can be stated that pyrimidinophanes are promising lead scaffold structures for further design of specific ligands for the PAS of AChE. Also AChE inhibitors with a 6-methyluracil moiety may be considered as potential drugs for the treatment of pathological muscle weakness syndromes.

Inhibitory potential of Rosa canina and Rosa sempervirens fruit extracts towards acetylcholinesterase

Acetylcholinesterase (AChE) is a key enzyme catalysing the hydrolysis of acetylcholine in the nervous system. The inhibitors of AChE are used in treatment of Alzheimer's disease. Due to numerous side effects of synthetic AChE inhibitors, there is a great need for new inhibitors, preferably from natural sources. Thus, the aim of this study was to examine AChE inhibitory potential of water and methanol fruit extracts of Rosa canina L., traditionally used in folk medicine, and poorly investigated Rosa sempervirens L. The inhibitory effect of the extracts was evaluated using a modified in vitro spectrophotometric Ellman's method [1]. During the method optimization, it was tested how buffers (Tris-HCl and phosphate buffer), frequently used in the assay, and solvents used for plant extract dilution (DMSO, methanol, ethanol, water) affect the enzyme activity. The results suggest that the use of 20 mM Tris-HCl pH 8 as a buffer and water as a solvent had the lowest influence on AChE activity, so they were chosen as optimal. All investigated extracts of R. sempervirens expressed greater activity than those of R. canina. Methanol dry fruit extract of R. sempervirens expressed the highest activity (IC50 = 1.2 mg mL-1), while water fresh fruit extract of R. canina exhibited the lowest AChE inhibitory potential. In comparison with galantamine, a well-known potent inhibitor of AChE but with adverse effects, all extracts manifested weaker activity.

Luminescent silica nanoparticles for sensing acetylcholinesterase-catalyzed hydrolysis of acetylcholine

This work highlights the H-function of Tb(III)-doped silica nanoparticles in aqueous solutions of acetic acid as a route to sense acetylcholinesterase-catalyzed hydrolysis of acetylcholine (ACh). The H-function results from H+-induced quenching of Tb(III)-centered luminescence due to protonation of Tb(III) complexes located close to silica/water interface. The H-function can be turned on/switched off by the concentration of complexes within core or nanoparticle shell zones, by the silica surface decoration and adsorption of both organic and inorganic cations on silica surface. Results indicate the optimal synthetic procedure for making nanoparticles capable of sensing acetic acid produced by enzymatic hydrolysis of acetylcholine. The H-function of nanoparticles was determined at various concentrations of ACh and AChE. The measurements show experimental conditions for fitting the H-function to Michaelis–Menten kinetics. Results confirm that reliable fluorescent monitoring AChE-catalyzed hydrolysis of ACh is possible through the H-function properties of Tb(III)-doped silica nanoparticles.

The effect of caffeic acid phenethyl ester (CAPE) on metabolic enzymes including acetylcholinesterase, butyrylcholinesterase, glutathione S-transferase, lactoperoxidase, and carbonic anhydrase isoenzymes I, II, IX, and XII

Caffeic acid phenethyl ester (CAPE) is an active component of honeybee propolis extracts. Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread and intensively studied metalloenzymes present in higher vertebrates including humans as many diverse isoforms. Acetylcholinesterase (AChE) is responsible for acetyl choline (ACh) hydrolysis and plays a fundamental role in nerve impulse transmission by terminating the action of the ACh neurotransmitter at cholinergic synapses and neuromuscular junctions. Butyrylcholinesterase (BChE) is another enzyme abundantly present in the liver and released into blood in a soluble form. Lactoperoxidase (LPO) is an enzyme involved in fighting pathogenic microorganisms whereas glutathione S-transferases (GSTs) are dimeric proteins present both in prokaryotic and eukaryotic organisms and involved in cellular detoxification mechanisms. In the present study, the inhibition effect of CAPE on human carbonic anhydrase (hCA) isoforms I, II, IX, and XII, AChE, BChE, LPO, and GST was evaluated. CAPE inhibited these enzymes with Kis in the range between micromolar to picomolar. The best inhibitory effect was observed against AChE and BChE.

Cholinergic Toxicity

Cholinergic drugs exert their functions by inhibiting acetylcholinesterase, the enzyme responsible for hydrolyzing acetylcholine and ending neuronal or neuromuscular neurotransmission. These compounds are used in clinical medicine to treat various disorders, as pesticides, and as weapons of mass destruction. This review describes the drugs that affect the cholinergic system and discusses stabilization, diagnosis and definitive therapy, principles and controversies of definitive care, and disposition and outcomes for these agents. Figures show acetylcholinesterase hydrolysis of acetylcholine, neurotransmission in the nervous system, the mechanism of inhibition of acetylcholinesterase by an organophosphorus (OP) compound, and the general chemical structure of thion OP and oxon OP agents and carbamates. Tables list OP pesticides associated with OP-induced delayed neuropathy, the effects of cholinesterase inhibition, the symptoms of cholinergic poisoning according to severity, and a treatment algorithm for acetylcholinesterase poisoning. This review contains 4 highly rendered figures, 4 tables, and 85 references.

Cholinergic Toxicity

Cholinergic drugs exert their functions by inhibiting acetylcholinesterase, the enzyme responsible for hydrolyzing acetylcholine and ending neuronal or neuromuscular neurotransmission. These compounds are used in clinical medicine to treat various disorders, as pesticides, and as weapons of mass destruction. This review describes the drugs that affect the cholinergic system and discusses stabilization, diagnosis and definitive therapy, principles and controversies of definitive care, and disposition and outcomes for these agents. Figures show acetylcholinesterase hydrolysis of acetylcholine, neurotransmission in the nervous system, the mechanism of inhibition of acetylcholinesterase by an organophosphorus (OP) compound, and the general chemical structure of thion OP and oxon OP agents and carbamates. Tables list OP pesticides associated with OP-induced delayed neuropathy, the effects of cholinesterase inhibition, the symptoms of cholinergic poisoning according to severity, and a treatment algorithm for acetylcholinesterase poisoning. This review contains 4 highly rendered figures, 4 tables, and 85 references.

Organophosphorus Inhibition and Characterization of Recombinant Guinea Pig Acetylcholinesterase.

Organophosphorus (OP) pesticides and nerve agents have been designed to inhibit the hydrolysis of the neurotransmitter acetylcholine by covalently binding to the active site serine of acetylcholinesterase while Alzheimer drugs and prophylactics, such as tacrine, are characterized by reversible binding. Historically, the guinea pig has been believed to be the best non-primate model for OP toxicology and medical countermeasure development because, similarly to humans, guinea pigs have low amounts of circulating OP metabolizing carboxylesterase. To explore the hypothesis that guinea pigs are the appropriate responder species for OP toxicology and medical countermeasure development, guinea pig acetylcholinesterase (gpAChE) was cloned into pENTR/D-TOPO, recombined into pT-Rex-DEST30 and expressed in Human Embryonic Kidney 293 cells. Recombinant gpAChE was purified to a specific activity of 800 U/mg using size exclusion and immobilized nickel affinity chromatography, with purity confirmed by gel electrophoresis. Ellman's assay was used to enzymatically characterize gpAChE, identifying a K(M) of 154±18.7 µmol L(-1) and a k(cat) of 4.79x10(4)±5.26x10(2) /sec. Apparent gpAChE IC50's for diisopropylfluorophosphate, dicrotophos, paraoxon, and an Alzheimer's drug, tacrine, were found to be 10.1±1.98, 337±108, 1.02±0.29 and 0.30±0.01 µmol L(-1), respectively. Apparent gpAChE inhibition constants for diisopropylfluorophosphate, dicrotophos, paraoxon, and tacrine were found to be 8.40±0.60, 4.50±0.30, 0.29±0.01 and 0.42±0.07 µmol L(-1), respectively. Lineweaver-Burk plots confirmed tacrine as a mixed inhibitor and paraoxon, dicrotophos and diisopropylfluorophosphate as irreversible non-competitive inhibitors. gpAChE bimolecular rate constants for diisopropylfluorophosphate, dicrotophos and paraoxon were found to be 1.44±0.33x10(4), 1.56±0.12x10(3) and 4.57± 0.23x10(5) L µmol(-1) min(-1), respectively. Although the blood levels of OP metabolizing carboxylesterases in the guinea pig are similar to the low levels in human blood, the gpAChE is different in its enzymology. Therefore, medical countermeasures against OP intoxication should be tested for efficacy with the recombinant form of gpAChE prior to initiating animal studies.

Bone status of acetylcholinesterase-knockout mice

Acetylcholinesterase (AChE) hydrolyzes acetylcholine (ACh) to acetate and choline and thereby terminates nerve impulse transmission. ACh is also expressed in bone tissue and enhances here proliferation and differentiation of osteoblasts, which makes it interesting to investigate effects of AChE deficiency on bone. To our knowledge, this is the first study that analyzed bone of heterozygous acetylcholinesterase-knockout (AChE-KO) mice.Tibia, femur, thoracic and lumbar vertebrae of 16-week-old female heterozygous AChE-KO mice and their corresponding wildtypes (WT) were analyzed using real-time RT-PCR, dual-energy X-ray absorptiometry, biomechanics, micro-computed tomography, histology and histomorphometry.Our data revealed that heterozygous AChE-KO did not cause negative effects upon bone parameters analyzed. In contrast, the number of osteoclasts per perimeter was significantly reduced in lumbar vertebrae. In addition, we found a significant decrease in trabecular perimeter of lumbar vertebrae and cortical area fraction (Ct.Ar/Tt.Ar) in the mid-diaphysis of femurs of AChE-KO mice compared to their WT. Therefore, presumably a local homozygous knockout of AChE or AChE-inhibitor administration might be beneficial for bone formation due to ACh accumulation. However, many other bone parameters analyzed did not differ statistically significantly between AChE-KO and WT mice. That might be reasoned by the compensating effect of butyrylcholinesterase (BChE).

Acetylcholinesterase immobilized on modified magnetic beads as a tool for screening a compound library

Acetylcholinesterase (AChE) from Electrophorus electricus was immobilized on the surface of amino-modified magnetic beads (AChE-MB), and its activity evaluated by the quantification of acetylcholine hydrolysis. A reference mixture composed of AChE binders (galanthamine and a probe coumarin, K i = 0.031 ± 0.010 μM) and non-binders (ketamine and propranolol) was used to probe the fishing assay. The performance of the bioconjugation assay was demonstrated with a library of 12 reference coumarins from which two ligands were directly identified by LC-MS/MS in a single assay, demonstrating the usefulness of this approach.

Liquid crystal sensor for the detection of acetylcholine using acetylcholinesterase immobilized on a nanostructured polymeric surface

In this study, we report on a label-free biosensor for the detection of acetylcholine (ACh) and an acetylcholinesterase (AChE) inhibitor, utilizing liquid crystals (LCs) on a polymeric surface with periodic nanostructures. The polymeric nanostructures, which hold sinusoidal anisotropic patterns, were fabricated by a sequential process of poly(dimethylsiloxane) buckling and replication of these patterns on a poly(urethane acrylate) surface where a film of gold was deposited. AChE was then covalently immobilized onto the gold surface. Optical images of nematic 4-cyano-4′-pentylbiphenyl (5CB) revealed that it aligned parallel to the plane of the enzyme-decorated surface. However, AChE-mediated hydrolysis of ACh resulted in a plume of choline, acetate, and unreacted ACh, which in turn produced a distinctive optical transition of 5CB (from uniform to random) by masking the anisotropic surface topography. The hydrolysis of ACh was inhibited in the presence of a carbamate insecticide (AChE inhibitor), which prevented the orientational transition of 5CB by decreasing the enzymatic activity of AChE. These results suggest that this LC-based enzymatic sensor is highly sensitive to ACh and the AChE inhibitor, with a detection limit of 10 and 1 nM, respectively. This study demonstrates that polymeric surfaces with continuous wavy features can be used as LC-based biosensors to amplify the existence of ACh and an AChE inhibitor without labeling or an additional amplification strategy.

Novel aspects of cholinergic regulation of colonic ion transport.

Nicotinic receptors are not only expressed by excitable tissues, but have been identified in various epithelia. One aim of this study was to investigate the expression of nicotinic receptors and their involvement in the regulation of ion transport across colonic epithelium. Ussing chamber experiments with putative nicotinic agonists and antagonists were performed at rat colon combined with reverse transcription polymerase chain reaction (RT-PCR) detection of nicotinic receptor subunits within the epithelium. Dimethylphenylpiperazinium (DMPP) and nicotine induced a tetrodotoxin-resistant anion secretion leading to an increase in short-circuit current (Isc) across colonic mucosa. The response was suppressed by the nicotinic receptor antagonist hexamethonium. RT-PCR experiments revealed the expression of α2, α4, α5, α6, α7, α10, and β4 nicotinic receptor subunits in colonic epithelium. Choline, the product of acetylcholine hydrolysis, is known for its affinity to several nicotinic receptor subtypes. As a strong acetylcholinesterase activity was found in colonic epithelium, the effect of choline on Isc was examined. Choline induced a concentration-dependent, tetrodotoxin-resistant chloride secretion which was, however, resistant against hexamethonium, but was inhibited by atropine. Experiments with inhibitors of muscarinic M1 and M3 receptors revealed that choline-evoked secretion was mainly due to a stimulation of epithelial M3 receptors. Although choline proved to be only a partial agonist, it concentration-dependently desensitized the response to acetylcholine, suggesting that it might act as a modulator of cholinergically induced anion secretion. Thus the cholinergic regulation of colonic ion transport – up to now solely explained by cholinergic submucosal neurons stimulating epithelial muscarinic receptors – is more complex than previously assumed.

PH-dependent hydrolysis of acetylcholine: Consequences for non-neuronal acetylcholine

Acetylcholine is inactivated by acetylcholinesterase and butyrylcholinesterase and thereby its cellular signalling is stopped. One distinguishing difference between the neuronal and non-neuronal cholinergic system is the high expression level of the esterase activity within the former and a considerably lower level within the latter system. Thus, any situation which limits the activity of both esterases will affect the non-neuronal cholinergic system to a much greater extent than the neuronal one. Both esterases are pH-dependent with an optimum at pH above 7, whereas at pH values below 6 particularly the specific acetylcholinesterase is more or less inactive. Thus, acetylcholine is prevented from hydrolysis at such low pH values. The pH of the surface of the human skin is around 5 and therefore non-neuronal acetylcholine released from keratinocytes can be detected in a non-invasive manner. Several clinical conditions like metabolic acidosis, inflammation, fracture-related haematomas, cardiac ischemia and malignant tumours are associated with local or systemic pH values below 7. Thus, the present article describes some consequences of an impaired inactivation of extracellular non-neuronal acetylcholine.

Effect of some Plants and Pesticides on Acetylcholinesterase

The principal role of acetylcholinesterase (AChE)is the termination of nerve impulse transmission at the cholinergic synapses by rapid hydrolysis of acetylcholine (ACh). Inhibition of AChE serves as a strategy for the treatment of Alzheimer's Disease (AD). Several acetylcholinesterase inhibitors (AChEIs) are used for the symptomatic treatment of AD A potential source of AChE inhibitors is certainly provided by the abundance of plants in nature. The aim of this article is study the effect of some plants and pesticides on acetylcholinesterase. Several plants considered as a source of acetylcholinesterase inhibitors and pesticides special organophosphorus. Cholinesterase inhibitors are the only approved drugs for treating patients with mild to moderately severe Alzheimer's disease, a disorder associated with progressive degeneration of memory and cognitive function. The memory impairment in patients with Alzheimer's disease results from a deficit of cholinergic function in the brain. The most important changes observed in the brain are a decrease in cortical levels of the neurotransmitter acetylcholine and associated enzyme choline transferees. Acetylcholinesterase inhibitors can restore the level of acetylcholine by inhibiting acetylcholinesterase. Principal role of acetyl cholinesterase (AChE) is the termination of nerve impulse transmission at the cholinergic synapses by rapid hydrolysis of acetylcholine (ACh). Inhibition of AChE serves as a strategy for the treatment of Alzheimer's Disease (AD), senile dementia, ataxia, myasthenia gravis and Parkinson's disease (Kumar et al., 2011). There are a few synthetic medicines, e.g., tacrine, donepezil and the natural product-based rivastigmine for treatment of cognitive dysfunction and memory loss associated with AD. There are two types of cholinesterase, AChE and butyrylcholinestrase (BuChE). The AChE is found primarily in the blood and neural synapses. The BuChE is found primarily in the liver. The biggest difference between the two is the substrates. The AChE hydrolyzes acetylcholine (ACh) more quickly and BuChE hydrolyzes butyrylcholine (BuCh) more quickly. The BuCh is a synthetic compound used to distinguish AChE receptors from BuChE receptors. Many of the drugs that are available for treatment of AD target both AChE and BuChE but some are more (Mehta et al., 2012). These compounds have been reported to have their adverse effects including gastrointestinal disturbances and problems associated with bioavailability, which necessitates the interest in finding better AChE inhibitors from natural resources. In traditional practices numerous plants have been used to treat cognitive disorders, including neurodegenerative diseases and different neuron pharmacological disorders.

Fluorescein-5-isothiocyanate-conjugated protein-directed synthesis of gold nanoclusters for fluorescent ratiometric sensing of an enzyme-substrate system.

This study describes the synthesis of a dual emission probe for the fluorescent ratiometric sensing of hydrogen peroxide (H2O2), enzyme activity, and environmental pH change. Green-emitting fluorescein-5-isothiocyanate (FITC) was conjugated to the amino groups of bovine serum albumin (BSA). This FITC-conjugated BSA acted as a template for the synthesis of red-emitting gold nanoclusters (AuNCs) under alkaline conditions. Under single wavelength excitation, FITC/BSA-stabilized AuNCs (FITC/BSA-AuNCs) emitted fluorescence at 525 and 670nm, which are sensitive to changes in solution pH and H2O2 concentration, respectively. The effective fluorescence quenching of AuNCs by H2O2 enabled FITC/BSA-AuNCs to ratiometrically detect the H2O2 product-related enzyme system and its inhibition, including glucose oxidase-catalyzed oxidation of glucose, acetylcholinesterase/choline oxidase-mediated hydrolysis and oxidation of acetylcholine, and paraoxon-induced inhibition of acetylcholinesterase activity. When pH-insensitive AuNCs were used as an internal standard, FITC/BSA-AuNCs offered a sensitive and reversible ratiometric sensing of a 0.1-pH unit change in the pH range 5.0-8.5. The pH-induced change in FITC fluorescence enabled FITC/BSA-AuNCs to detect an ammonia product-related enzyme system. This was exemplified with the determination of urea in plasma by urease-mediated hydrolysis of urea.

Hydrophobic interactions in the pillar[5]arene-based host–guest complexation and their application in the inhibition of acetylcholine hydrolysis

The host–guest complexations between a water-soluble pillar[5]arenes (WP5) and choline derivatives with different alkyl chain lengths were investigated. The hydrophobic interactions played a significant role in these pillar[5]arene-based host–guest complexations. By taking advantage of hydrophobic interactions, the cavity of WP5 could be further employed to inhibit the hydrolysis of acetylcholine in the presence of acetylcholinesterase.

Modeling the Interaction betweenβ-Amyloid Aggregates and Choline Acetyltransferase Activity and Its Relation with Cholinergic Dysfunction through Two-Enzyme/Two-Compartment Model

The effect of β-amyloid aggregates on activity of choline acetyltransferase (ChAT) which is responsible for synthesizing acetylcholine (ACh) in human brain is investigated through the two-enzyme/two-compartment (2E2C) model where the presynaptic neuron is considered as compartment 1 while both the synaptic cleft and the postsynaptic neuron are considered as compartment 2 through suggesting three different kinetic mechanisms for the inhibition effect. It is found that the incorporation of ChAT inhibition by β-amyloid aggregates into the 2E2C model is able to yield dynamic solutions for concentrations of generated β-amyloid, ACh, choline, acetate, and pH in addition to the rates of ACh synthesis and ACh hydrolysis in compartments 1 and 2. It is observed that ChAT activity needs a high concentration of β-amyloid aggregates production rate. It is found that ChAT activity is reduced significantly when neurons are exposed to high levels of β-amyloid aggregates leading to reduction in levels of ACh which is one of the most significant physiological symptoms of AD. Furthermore, the system of ACh neurocycle is dominated by the oscillatory behavior when ChAT enzyme is completely inhibited by β-amyloid. It is observed that the direct inactivation of ChAT by β-amyloid aggregates may be a probable mechanism contributing to the development of AD.

In-vitro Screening for Acetylcholinesterase enzyme Inhibition potential and Antioxidant Activity of Extracts of Ipomoea Aquatica Forsk: Therapeutic lead for Alzheimer's disease

Alzheimer’s disease (AD) is a primary degenerative disease of the central nervous system. The progression of Alzheimer’s disease will ultimately lead to dementia, behavioral and cognitive impairments. Increased level of the enzyme acetylcholinesterase AChE plays a key role in hydrolysis of the neurotransmitter Acetylcholine (ACh) which worsen the condition of cognitive dysfunction. Several drug of natural origin are known to possess AChE inhibition and antioxidant activity .The main objective of the present study is to evaluate AChE inhibition and antioxidant activity of the plant Ipomoea Aquatica Forsk .Leaves of Ipomoea Aquatica Forsk was extracted with Chloroform, n-Hexane, Ethanol and mixture of Ethanol: water (6:4) (hydro-alcoholic extract) using soxhlet extraction. All the four extracts were examined for In-Vitro anti-cholinesterase by Ellman’s method and antioxidant activity by DPPH and Hydrogen peroxide radical scavenging assay. Results obtained from the study clearly demonstrates that all four extract has shown promising acetylcholinesterase inhibition activity in hydro alcoholic extract reveals the best inhibition potential with IC50 49.03 μg /ml .Similarly all the extracts projects significant antioxidant activity in DPPH assay with IC50 value ranging from 19.64 to 88.63 μg /ml and in Hydrogen peroxide assay with IC50 value ranging from 56.79 to 137.3 μg /ml.

Prevalence of Wild-Type Butyrylcholinesterase Genotype in Patients with Alzheimer’s Dementia

Approximately, two-thirds patients with Alzheimer’s disease (AD) are reported to have homozygous wild-type butyrylcholinesterase (BuChE) gene expression. It is associated with a higher rate of hydrolysis of acetylcholine, which ultimately leads to increase in the levels of BuChE in advanced stages of the disease. Rivastigmine, a dual inhibitor of acetylcholinesterase (AChE) and BuChE, might be of additional benefit in patients with AD with wild-type BuChE allele.

Molecular modeling and in vitro reactivation study between the oxime BI-6 and acetylcholinesterase inhibited by different nerve agents

Nerve agents are organophosphates acting as potent inhibitors of acetylcholinesterase (AChE), the enzyme responsible for the hydrolysis of acetylcholine and, consequently, the termination of the transmission of nerve impulses. The inhibition of AChE by an organophosphate can be reversed by a nucleophilic agent able to dephosphorylate a serine residue in the active site of AChE. In this sense, the oximes are compounds capable of removing the nerve agent and reactivate the enzyme. Here, we have applied a methodology involving theoretical docking and Quantum Mechanics/Molecular Mechanics, using the softwares Molegro® and Spartan®, to evaluate the kinetic constants of reactivation and the interactions of the oxime BI-6 with AChE inhibited by different organophosphorus compounds in comparison to in vitro data. Results confirm that this method is suitable for the prediction of kinetic and thermodynamic parameters of oximes, which may be useful in the design and selection of new and more effective oximes.

CHEMICAL WARFARE: PERSPECTIVES ON REACTIVATING THE ENZYME ACETYLCHOLINESTERASE INHIBITED BY ORGANOPHOSPHATES

Summary It is known that nerve agents are potent inhibitors of acetylcholinesterase (AChE), the enzyme responsible for the hydrolysis of the neurotransmitter acetylcholine and, thus, transmission of nerve impulses. The process of AChE inhibition by nerve agents can be reversed by a nucleophile able to dephosphorylate the enzyme. In this sense, oximes exhibit this characteristic and are able to remove the neurotoxic and reactivate AChE. Here, we review experimental and theoretical results involving docking and quantum mechanical-molecular mechanics hybrid methods (QM/MM), using Molegro ® and Spartan ® softwares to analyze the interaction of different nerve agents and oximes with AChE and to evaluate kinetic constants of reactivation.