Acetylthiocholine
Acetylcholinesterase
Cholinesterases
Tetraisopropylpyrophosphamide
Cholinesterase Inhibitors
Thiocholine
Histochemically distinct compartments in the striatum of human, monkeys, and cat demonstrated by acetylthiocholinesterase staining. (1/38)
We here report observations on the distribution of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) in the striatum of the adult human, the rhesus monkey, and the cat. By the histochemical staining methods of Geneser-Jensen and Blackstad and of Karnovsky and Roots, compartments of low cholinesterase activity were identified in parts of the striatum in all three species. In frontal sections, these enzyme-poor zones appeared as a variable number of weakly stained approximately 0.5-mm-wide zones embedded in a darkly stained background. The zones varied in cross-sectional shape from round to elongated and were sometimes branched. They were most prominent in the head of the caudate nucleus. Three-dimensional reconstructions of serial sections through the caudate nucleus in the human and cat suggest that over distances of at least several millimeters, the zones of low enzyme activity form nearly continuous labyrinths. (+info)Determinants of substrate specificity of a second non-neuronal secreted acetylcholinesterase from the parasitic nematode Nippostrongylus brasiliensis. (2/38)
We recently reported on a non-neuronal secreted acetylcholinesterase (AChE B) from the nematode parasite Nippostrongylus brasiliensis. Here we describe the primary structure and enzymatic properties of a second secreted variant, termed AChE C after the designation of native AChE isoforms from this parasite. As for the former enzyme, AChE C is truncated at the carboxyl terminus in comparison with the Torpedo AChE, and three of the 14 aromatic residues that line the active site gorge are substituted by nonaromatic residues, corresponding to Tyr70 (Ser), Trp279 (Asn) and Phe288 (Met). A recombinant form of AChE C was highly expressed by Pichia pastoris. The enzyme was monomeric and hydrophilic, and displayed a marked preference for acetylthiocholine as substrate. A double mutation (W302F/W345F, corresponding to positions 290 and 331 in Torpedo) rendered the enzyme 10-fold less sensitive to excess substrate inhibition and two times less susceptible to the bis quaternary inhibitor BW284C51, but did not radically affect substrate specificity or sensitivity to the 'peripheral site' inhibitor propidium iodide. In contrast, a triple mutant (M300G/W302F/W345F) efficiently hydrolysed propionylthiocholine and butyrylthiocholine in addition to acetylthiocholine, while remaining insensitive to the butyrylcholinesterase-specific inhibitor iso-OMPA and displaying a similar profile of excess substrate inhibition as the double mutant. These data highlight a conserved pattern of active site architecture for nematode secreted AChEs characterized to date, and provide an explanation for the substrate specificity that might otherwise appear inconsistent with the primary structure in comparison to other invertebrate AChEs. (+info)High-resolution optical mapping of the right bundle branch in connexin40 knockout mice reveals slow conduction in the specialized conduction system. (3/38)
Connexin40 (Cx40) is a major gap junction protein that is expressed in the His-Purkinje system and thought to be a critical determinant of cell-to-cell communication and conduction of electrical impulses. Video maps of the ventricular epicardium and the proximal segment of the right bundle branch (RBB) were obtained using a high-speed CCD camera while simultaneously recording volume-conducted ECGs. In Cx40(-/-) mice, the PR interval was prolonged (47.4+/-1.4 in wild-type [WT] [n=6] and 57.5+/-2.8 in Cx40(-/-) [n=6]; P<0.01). WT ventricular epicardial activation was characterized by focused breakthroughs that originated first on the right ventricle (RV) and then the left ventricle (LV). In Cx40(-/-) hearts, the RV breakthrough occurred after the LV breakthrough. Additionally, Cx40(-/-) mice showed RV breakthrough times that were significantly delayed with respect to QRS complex onset (3.7+/-0.7 ms in WT [n=6] and 6.5+/-0.7 ms in Cx40(-/-) [n=6]; P<0.01), whereas LV breakthrough times did not change. Conduction velocity measurements from optical mapping of the RBB revealed slow conduction in Cx40(-/-) mice (74.5+/-3 cm/s in WT [n=7] and 43.7+/-6 cm/s in Cx40(-/-) [n=7]; P<0.01). In addition, simultaneous ECG records demonstrated significant delays in Cx40(-/-) RBB activation time with respect to P time (P-RBB time; 41.6+/-1.9 ms in WT [n=7] and 55.1+/-1.3 ms in [n=7]; P<0.01). These data represent the first direct demonstration of conduction defects in the specialized conduction system of Cx40(-/-) mice and provide new insight into the role of gap junctions in cardiac impulse propagation. (+info)Action potential characteristics and arrhythmogenic properties of the cardiac conduction system of the murine heart. (4/38)
Studies have characterized conduction velocity in the right and left bundle branches (RBB, LBB) of normal and genetically engineered mice. However, no information is available on the action potential characteristics of the specialized conduction system (SCS). We have used microelectrode techniques to characterize action potential properties of the murine SCS, as well as epicardial and endocardial muscle preparations for comparison. In the RBB, action potential duration at 50%, 70%, and 90% repolarization (APD(50,70,90)) was 6+/-0.7, 35+/-6, and 90+/-7 ms, respectively. Maximum upstroke velocity (dV/dt(max)) was 153+/-14 V/s, and conduction velocity averaged 0.85+/-0.2 m/s. APD(90) was longer in the Purkinje network of fibers (web) than in the RBB (P<0.01). Web APD(50) was longer in the left than in the right ventricle (P<0.05). Yet, web APD(90) was longer in the right than in the left ventricle (P<0.001). APD(50,70) was significantly longer in the endocardial than in the epicardial (P<0.001; P<0.003). APD(90) in the epicardial and endocardial was shorter than in the RBB ( approximately 36 ms versus approximately 100 ms). Spontaneous electrical oscillations in phase 2 of the SCS occasionally resulted in early afterdepolarizations. These results demonstrate that APDs in the murine SCS are significantly ( approximately 2-fold) longer than in the myocardium and implicate the role of the murine SCS in arrhythmias. The differences should have important implications in the use of the mouse heart to study excitation, propagation, and arrhythmias. (+info)Reversibly bound and covalently attached ligands induce conformational changes in the omega loop, Cys69-Cys96, of mouse acetylcholinesterase. (5/38)
We have used a combination of cysteine substitution mutagenesis and site-specific labeling to characterize the structural dynamics of mouse acetylcholinesterase (mAChE). Six cysteine-substituted sites of mAChE (Leu(76), Glu(81), Glu(84), Tyr(124), Ala(262), and His(287)) were labeled with the environmentally sensitive fluorophore, acrylodan, and the kinetics of substrate hydrolysis and inhibitor association were examined along with spectroscopic characteristics of the acrylodan-conjugated, cysteine-substituted enzymes. Residue 262, being well removed from the active center, appears unaffected by inhibitor binding. Following the binding of ligand, hypsochromic shifts in emission of acrylodan at residues 124 and 287, located near the perimeter of the gorge, reflect the exclusion of solvent and a hydrophobic environment created by the associated ligand. By contrast, the bathochromic shifts upon inhibitor binding seen for acrylodan conjugated to three omega loop (Omega loop) residues 76, 81, and 84 reveal that the acrylodan side chains at these positions are displaced from a hydrophobic environment and become exposed to solvent. The magnitude of fluorescence emission shift is largest at position 84 and smallest at position 76, indicating that a concerted movement of residues on the Omega loop accompanies gorge closure upon ligand binding. Acrylodan modification of substituted cysteine at position 84 reduces ligand binding and steady-state kinetic parameters between 1 and 2 orders of magnitude, but a similar substitution at position 81 only minimally alters the kinetics. Thus, combined kinetic and spectroscopic analyses provide strong evidence that conformational changes of the Omega loop accompany ligand binding. (+info)Asymmetric distribution of acetylcholinesterase in gravistimulated maize seedlings. (6/38)
Acetylcholinesterase (AChE) activity has previously been studied by this laboratory and shown to occur at the interface between the stele and cortex of the mesocotyl of maize (Zea mays L.) seedlings. In this work we studied the distribution of AChE activity in 5-d-old maize seedlings following a gravity stimulus. After the stimulus, we found an asymmetric distribution of the enzyme in the coleoptile, the coleoptile node, and the mesocotyl of the stimulated seedlings using both histochemical and colorimetric methods for measuring the hydrolysis of acetylthiocholine. The hydrolytic capability of the esterase was greater on the lower side of the horizontally placed seedlings. Using the histochemical method, we localized the hydrolytic capability in the cortical cells around the vascular stele of the tissues. The hydrolytic activity was inhibited 80 to 90% by neostigmine, an inhibitor of AChE. When neostigmine was applied to the corn kernel, the gravity response of the seedling was inhibited and no enzyme-positive spots appeared in the gravity-stimulated seedlings. We believe these results indicate a role for AChE in the gravity response of maize seedlings. (+info)Studies of the acetylcholinesterase from houseflies (Musca domestica L.) resistant and susceptible to organophosphorus insecticides. (7/38)
Acetylcholinesterase from the heads of insecticide-resistant and -susceptible houseflies (Musca domestica L.) was studied in vitro. The enzymes could not be distinguished electrophoretically, and their behaviour on polyacrylamide-disc-gel electrophoresis was influenced by the presence of Triton X-100 in both the homogenate and the gels. In the absence of detergent, the acetylcholinesterase was heterogeneous, but behaved as a single enzyme when it was present. By analogy with studies of acetylcholinesterase from other sources, these observations were attributed to aggregation of the enzyme when not bound by membranes. The enzyme from resistant flies was more slowly inhibited than the susceptible enzyme, bimolecular rate constants (ki) differing by approx. 4-20-fold for a range of organophosphorus compounds. The kinetics of inhibition of acetylcholinesterase were consistent with the results of electrophoresis, i.e. they corresponded to those of a single enzyme in the presence of Triton X-100, but a mixture of enzymes in its absence. The susceptibility of the more sensitive components in these mixtures was determined. (+info)Substrate activation in acetylcholinesterase induced by low pH or mutation in the pi-cation subsite. (8/38)
Substrate inhibition is considered a defining property of acetylcholinesterase (AChE), whereas substrate activation is characteristic of butyrylcholinesterase (BuChE). To understand the mechanism of substrate inhibition, the pH dependence of acetylthiocholine hydrolysis by AChE was studied between pH 5 and 8. Wild-type human AChE and its mutants Y337G and Y337W, as well as wild-type Bungarus fasciatus AChE and its mutants Y333G, Y333A and Y333W were studied. The pH profile results were unexpected. Instead of substrate inhibition, wild-type AChE and all mutants showed substrate activation at low pH. At high pH, there was substrate inhibition for wild-type AChE and for the mutant with tryptophan in the pi-cation subsite, but substrate activation for mutants containing small residues, glycine or alanine. This is particularly apparent in the B. fasciatus AChE. Thus a single amino acid substitution in the pi-cation site, from the aromatic tyrosine of B. fasciatus AChE to the alanine of BuChE, caused AChE to behave like BuChE. Excess substrate binds to the peripheral anionic site (PAS) of AChE. The finding that AChE is activated by excess substrate supports the idea that binding of a second substrate molecule to the PAS induces a conformational change that reorganizes the active site. (+info)Acetylthiocholine is a chemical compound that is used as a neurotransmitter in the nervous system. It is a derivative of acetylcholine, which is a neurotransmitter that is involved in muscle movement and other functions. Acetylthiocholine is produced in the body when acetylcholine is broken down, and it is thought to play a role in the regulation of acetylcholine levels in the brain and other parts of the nervous system. In the medical field, acetylthiocholine is sometimes used as a diagnostic tool to test for certain types of neurological disorders, such as myasthenia gravis, which is a condition that affects the muscles and causes weakness and fatigue.
Acetylcholinesterase (AChE) is an enzyme that is responsible for breaking down the neurotransmitter acetylcholine (ACh) in the nervous system. ACh is a chemical messenger that is used to transmit signals between nerve cells, and AChE plays a critical role in regulating the levels of ACh in the synaptic cleft, the small gap between nerve cells where signaling occurs. In the medical field, AChE is often studied in the context of diseases that affect the nervous system, such as Alzheimer's disease, myasthenia gravis, and certain types of nerve damage. In these conditions, the activity of AChE may be altered, leading to changes in the levels of ACh in the brain and other parts of the nervous system. AChE inhibitors are drugs that are used to treat certain neurological disorders by slowing down the breakdown of ACh, thereby increasing its levels in the brain. These drugs are commonly used to treat Alzheimer's disease and myasthenia gravis, among other conditions.
Cholinesterases are a group of enzymes that break down the neurotransmitter acetylcholine in the body. There are two main types of cholinesterases: acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Acetylcholinesterase is primarily found in the synaptic clefts of nerve cells, where it breaks down acetylcholine after it has transmitted a signal across the synapse. This helps to terminate the signal and prevent overstimulation of the postsynaptic neuron. Butyrylcholinesterase is found in a variety of tissues throughout the body, including the liver, kidney, and blood. It is also found in the brain, where it plays a role in the breakdown of acetylcholine and other neurotransmitters. In the medical field, cholinesterases are important because they are often used as markers of organ function and can be used to diagnose certain diseases. For example, low levels of acetylcholinesterase activity in the blood can be a sign of organ damage or dysfunction, while high levels of butyrylcholinesterase activity can be a sign of liver disease. Cholinesterase inhibitors are also used as medications to treat certain neurological conditions, such as Alzheimer's disease and myasthenia gravis.
Tetraisopropylpyrophosphamide (TIP) is a medication that was previously used to treat certain types of cancer, such as Hodgkin's lymphoma and non-Hodgkin's lymphoma. It is a type of chemotherapy drug that works by interfering with the growth and division of cancer cells. However, TIP is no longer used for cancer treatment due to its toxic side effects and the availability of more effective and safer treatments. It is important to note that TIP is not a cure for cancer and should only be used under the guidance of a qualified healthcare professional.
Thiocholine is a chemical compound that is formed when choline, a neurotransmitter, is metabolized by the enzyme choline kinase. It is a precursor to the neurotransmitter acetylcholine and is involved in the regulation of muscle movement and memory. In the medical field, thiocholine is used as a diagnostic tool in the detection of certain liver and bile duct disorders, as well as in the treatment of certain types of cancer. It is also used as a contrast agent in imaging studies, such as magnetic resonance cholangiopancreatography (MRCP), to visualize the bile ducts and liver.
Butyrylcholinesterase (BuChE) is an enzyme that plays a crucial role in the breakdown of acetylcholine, a neurotransmitter that is involved in many important bodily functions. BuChE is primarily found in the blood and in the liver, but it is also present in other tissues throughout the body. In the medical field, BuChE is often measured as a way to assess liver function, as the enzyme is produced by liver cells. Abnormal levels of BuChE can be an indication of liver disease or other conditions that affect liver function. BuChE is also used as a biomarker for exposure to certain toxins, such as pesticides and heavy metals. In addition, researchers are studying BuChE as a potential target for the development of new drugs for the treatment of neurological disorders, such as Alzheimer's disease.
Acetylthiocholine
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- Substrates for the assay included acetylthiocholine (ATC) and butyrylthiocholine (BTC). (cdc.gov)
Acetylcholinesterase1
- 16. An amperometric acetylthiocholine sensor based on immobilization of acetylcholinesterase on a multiwall carbon nanotube-cross-linked chitosan composite. (nih.gov)