Showing papers on "Acetylthiocholine published in 2018"

Why is the hydrolytic activity of acetylcholinesterase pH dependent? Kinetic study of acetylcholine and acetylthiocholine hydrolysis catalyzed by acetylcholinesterase from electric eel.

Abstract: Abstract The dependence of the activity of acetylcholinesterase from electric eel at a pH value range of 4.8–9.8 (phosphate buffer), regarding acetylcholine and acetylthiocholine hydrolysis, was determined at 25 °C, ionic strength of 0.11 M, and initial substrate concentration of 4 mM. At a pH range of 4.8–9.8, the dependences A(pH) form a sigmoid increasing curve with the maximum catalytic activity at a pH range 8–9.5. For acetylcholine hydrolysis, the kinetic reason for such an increase in A consists mainly of an increase in the rate constant k2 (Michaelis-Menten) model with increasing pH of the reaction mixture. For acetylthiocholine hydrolysis, the kinetic explication of the determined dependence A(pH) is more complicated.

Determination of pesticides using a low-temperature co-fired ceramic microfluidic platform

Abstract: The aim of this work is the integration of an improved graphite–epoxy composite electrode modified with the acetylcholinesterase enzyme as a detector into a green tape ceramic microfluidic device for the online amperometric determination of pesticides. First, the operational conditions of the microfluidic system were optimized for the enzymatic substrate determination of acetylthiocholine. Good results were achieved for acetylthiocholine determination, obtaining a low detection limit and optimal sensitivity. The analytical performance of the microanalyzer was evaluated with organophosphorus and carbamate pesticides across a wide concentration range. Pesticides were determined indirectly measuring the enzymatic inhibition effect that they caused. The analysis was based on stopped-flow methodology with a three-step strategy: enzymatic substrate measurement, enzymatic inhibition by pesticide contact with the biosensor, and enzymatic substrate measurement after the inhibition process. The pesticide co...

Enzymatic Inhibition Constant of Acetylcholinesterase for the Electrochemical Detection and Sensing of Chlorpyrifos

Abstract: Infiltration into soils of pesticides used during agricultural production has led to the contamination of aquatic ecosystems due to their long persistence in the environment. Some pesticides (e.g. Chlorpyrifos) are inhibitors of cholinesterase enzyme activity and their presence in water samples can be indirectly detected by a decrease in enzymatic activity. Biosensors based on cholinesterase enzymes are an alternative for the sensitive detection of important contaminants in the environmental sector. Acetylcholinesterase enzyme (AChE) catalyzes the hydrolysis of acetylthiocholine (ATCh) to produce thiocholine (TCh). This feature can be employed to measure the decrease in AChE activity. The inhibitory characteristics of the AChE-Chlorpyrifos system have been studied through cyclic voltammetry, by evaluation of the oxidation of the thiol group, which corresponds to TCh production on platinum electrodes in the presence of an inhibitor. In the present study, enzymatic curves were obtained at different concentrations of substrate and inhibitor, which were then used to determine the enzymatic kinetics corresponding to a mixed inhibition type, with an inhibition constant (Ki) of (18.26 ± 0.01) μM. TCh electrochemical detection appears to be a promising option for the development of biosensors to identify and quantify pesticides present in the ecosystem.

Synthesis and Biological Activity of (Z)-Dialkylaminoalkylamides of N-Benzoyl-α,β-Dehydroamino Acids and Their Iodomethylates

Abstract: A series of N,N-(dialkylamino)alkylamides of several N-substituted α,β-dehydroamino acids and their quaternary ammonium salts were synthesized via the reaction of unsaturated 5(4H)-oxazolones with N,N-dialkyldiamines and characterized by physicochemical characteristics. Their reactions with human erythrocytic acetylcholinesterase (ACE) and plasmic butyrylcholinesterase (BuCE) were studied. The IC50 values [concentration at which the hydrolysis rate of cholinesterase was 50% inhibited by acetylthiocholine (0.1 mM)] of all synthesized compounds were determined. It was found that all synthesized compounds possessed anticholinesterase activity and were specific mainly for BuCE.