Methyl parathion synergists

The oxidation, which is the bioactivation reaction, is inhibited by piperonyl butoxide, whereas the demethylation reaction catalyzed by glutathione transferase is not inhibited. Piperonyl butoxide is therefore an antagonist to methyl-parathion, but a synergist to most other pesticides, including carbamates and pyrethroids. Pyrethrins are very quickly detoxified by oxidation of one of the methyl groups, catalyzed by the CYP enzymes. 

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... 

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