Pesticides enzyme inhibition

Following work by the same group addressed some of the major problems arising when electrochemical biosensors are in contact with food matrices pH effect and particle effect. Both problems were solved treating the biosensor surface with a Tween20 /phosphate buffer solution (pH 7.5) after the incubation with pesticide. The treatment was successful in removing the particulate, the correct pH for enzyme activity measurement was attained and the pesticide enzyme inhibition... 

Toxin (Enzyme Inhibition) Biosensors Enzyme affectors (inhibitors and activators) that influence the rate of biocatalytic reactions can also be measured. Sensing probes for organophosphate and carbamate pesticides, for the respiratory... 

No data are available on platelet NTE activity in exposed subjects, and little data on lymphocyte NTE activity. In one reported case of suicidal poisoning with chlorpyrifos, inhibition of lymphocyte NTE was correlated with the enzyme inhibition in peripheral nerves (Osterloh et al., 1983). In another case of attempted suicide with the same compound, inhibition of NTE in peripheral lymphocytes was associated with the development of delayed neuropathy (Lotti, 1986). However, the threshold of NTE inhibition required for delayed neuropathy remains undetermined (Lotti, 1987). Observations in occupationally exposed subjects are limited in number, and more research is needed to investigate the applicability of NTE as a biomarker of exposure to OP pesticides. 

Mainly, two principles are used in electrochemical pesticide biosensor design, either enzyme inhibition or hydrolysis of pesticide. Among these two approaches inhibition-based biosensors have been widely employed in analysis due to the simplicity and wide availability of the enzymes. The direct enzymatic hydrolysis of pesticide is also extremely attractive for biosensing, because the catalytic reaction is superior and faster than the inhibition [27],... 

R. Kindervater, W. Kiinnecke, and R.D. Schimid, Exchangeable immobilized enzyme reactor for enzyme inhibition tests in flow-injection analysis using a magnetic device. Determination of pesticides in drinking water. Anal. Chim. Acta 234, 113-117 (1990). 

S. Jin, Z. Xu, J. Chen, X. Liang, Y. Wu, and X. Qian, Determination of organophosphate and carbamate pesticides based on enzyme inhibition using a pH-sensitive fluorescence probe. Anal. Chim. Acta 523, 117-123 (2004). 

Disulfoton and its breakdown products can be measured in the blood, urine, feces, liver, kidney, or body fat of exposed people. In cases of occupational or accidental exposure to disulfoton, the breakdown products are often measured in the urine. The breakdown products are relatively specific for disulfoton and a few other similar organophosphate pesticides and can be detected in urine for up to one week after people were last exposed. Because disulfoton inhibits cholinesterase in blood and in blood cells, inhibition of this enzyme activity may also suggest exposure to disulfoton. Cholinesterase activity in blood and in blood cells may remain inhibited for as long as 1-2 weeks after the last exposure. Because other organophosphate pesticides also inhibit cholinesterase activity in blood and blood cells, this test is not specific for disulfoton. The measurement of cholinesterase in blood and blood cells and the amount of disulfoton breakdown products in the urine cannot always predict how much disulfoton you were exposed to. Your doctor can send samples of your blood or urine to special laboratories that perform these tests. Chapters 2 and 6 provide more information about medical tests. 

Cortina, M., del Valle, M., and Marty, J.-L. (2008). Electronic tongue using an enzyme inhibition biosensor array for the resolution of pesticide mixtures. Electroanalysis 20(1), 54-60. 

A mode of action need not involve enzyme inhibition. It could be a simple physical action. Cholestyramine resins are used to form nonpolar aggregates with lipophilic substances. With this action they constitute a good antidote for pesticide poisoning and can serve as a prophylactic in... 

Like pesticides, heavy metals are traditionally tested by enzyme inhibition or modulation of catalytic activity. Several metalloproteins behave as chelators for specific metals with no known catalytic reactions. Such heavy metal binding sites exist in metallothioneins and in various protein elements of bacterial heavy metal mechanisms and have been exploited for specific detection through affinity events. Nevertheless and as previously mentioned, bacterial resistance mechanisms can also be linked to catalytic pathways. For instance, c5rtochromes c3 and hydrogenases from sulfate and sulfur reducing bacteria [284,285] are well suited for bioremediation purposes because they can reduce various metals such as U(V) and Cr(VI) [286,287]. Cytochrome c3 has been reported to catalyse Cr(VI) and U(VI) reduction in Desulfovibrio vulgaris [288,289], suggesting... 

One typical example of the high potential of pervaporation for boosting the selectivity of processes such as enzymic inhibition-based reactions is the method for the selective determination of pesticides in environmental samples. The method, which is only... 

F. Enzyme inhibition Enzymatic reactions can be surveyed on a TLC plate, and the end products detected. For example, cholinesterase-like enzymes in nervous tissue will catalyze the substrate indoxyl acetate to indoxol and acetic acid. In air, indoxol is converted to indigo blue, which can be visualized on a TLC plate. Some pesticides and insecticides inactivate enzymes associated with animal nervous tissue. The presence of minute amounts of such substances may interfere with the indoxyl acetate substrate reaction producing colorless spots on a blue background. For further details on enzyme inhibition TLC, see Ref. 63. 

Kindervater, R., Kfinnecke, W., Schmid, R. D., Exchangeable Immobilized Enzyme Reactor (EIMER) for Enzyme Inhibition Tests in FIA Using a Magnet Device. The Determination of Pesticides in Drinking Water , Anal. Chim Acta (1990) accepted. 

The primary mechanism of action of OP pesticides is inhibition of AChE. AChE is an enzyme found in the central nervous system (CNS) and the peripheral nervous system, and its normal physiologic action is to metabolize acetylcholine (ACh), a neurotransmitter. OPs inactivate AChE by phosphorylating the. serine hydroxyl group located at the active site of AChE. The phosphorylation occurs by loss of an OP leaving group and establishment of a covalent bond with AChE. 

Enzyme inhibition sensors are the most commonly reported enzyme-based biosensors for the detection of toxic compounds and heavy metal ions. The sensors are based on the selective inhibition of specific enzymes by classes of compounds or by the more general inhibition of enzyme activity. Most of the research carried out has been directed toward the detection of organophosphorus and carbamate insecticides and the triazine herbicides and metal ions analysis [72,73]. Several enzymes have been used in inhibition sensors for pesticides and heavy metal analysis using water, soil, and food samples including choline esterase, horseradish peroxidase, polyphenol oxidase, urease, and aldehyde dehydrogenase. 

Simonian A. L., Flounders A. W., and Wild J. R., FET-based biosensors for the direct detection of organophosphate neurotoxins. Electroanalysis, 16(22), 1896-1906, 2004. Sole S., Merkoci A., and Alegret S., Determination of toxic substances based on enzyme inhibition. Part I. Electrochemical biosensors for the determination of pesticides using batch procedures, Crit. Rev. Anal. Chem., 33(2), 89-126, 2003. 

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