Enzymes herbicides organophosphorus

The toxicant may react with an enzyme or a transport protein and inhibit its normal function. Enzymes may be inhibited by a compound that has a similar, but not identical structure as the true substrate instead of being processed, it blocks the enzyme. Typical toxicants of this kind are the carbamates and the organophosphorus insecticides that inhibit the enzyme acetyl cholinesterase. Some extremely efficient herbicides that inhibit enzymes important for amino acid synthesis in plants, e.g., glyphosate and glufosinate, are other good examples in this category. 

The herbicide atrazine is not toxic to midge (Chironomus tentans) larvae but has a strong synergistic effect on several organophosphorus insecHcides such as chlorpyrifos and parathion-methyl, but not to malathion. The increased rate of oxidahon to the achve toxicants, the oxons, is suggested as one of the mechanisms, and the level of CYP enzymes is elevated. Figure... 

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. 

Biological methods of detection have included enzyme inhibition for organophosphorus (OP) pesticides. After mobile-phase development, the layer is sprayed with esterase-1 Bacillus subtilis), followed by 1-thionaphthyl acetate substrate, and finally [2,2 -azo(l-naphthol-8-chloro-3,6-disulfonic acid) 4,4 -diphenyl disulfide] indicator to produce pink zones on a blue background with 0.05-5 ng minimum detection limits. Herbicides have been detected by inhibition of the Hill photosynthesis reaction. 

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