Research progresses on the metabolic mechanisms of organophosphate insecticides

The research progresses related to metabolic mechanisms of organophosphates(OPs) and metabolic resistance mechanisms of insects to organophosphates were summarized. The metabolic pathways of OPs in organisms and the metabolic enzymes involved in were described. OPs mainly experienced oxidation, hydrolysis and conjugation in organisms. The oxidation of OPs mainly occurred under the catalysis of cytochrome P450s. The most important oxidation reactions of OPs are desulfuration of organophosphorothioates(OPTs) to form organophosphate oxons, which exhibit higher toxicity to organisms than native OPTs, and dealkylation or dearylation of OPs. The OPs and its oxons could be hydrolyzed in organisms under the catalysis of phosphotriesterase including paraoxonase(PON1), and low toxic or non-toxic metabolites were produced. The conjunction of OPs is mainly catalyzed by glutathione S-transferases(GSTs). Changes in the metabolic ability to OPs in insects resulted in metabolic resistance. Gene overexpression or higher activity of cytochrome P450s, overexpression or gene mutation of esterases, and overexpression of glutathione S-transferases gene were related to the improved metabolism of OPs and contributed to the metabolic resistance to OPs such as diazinon and malathion in insects including Lucilia cuprina, Myzus persicae. Clarifying the metabolic mechanisms of OPs on the basis of OPs structures, metabolic pathways, the corresponding detoxification enzymes involved in, and the metabolic resistance mechanisms of OP-resistant insects, are very important for understanding the metabolic toxicology of OPs, safe and efficient application of OPs, controlling the OP-resistant insects, exploring and developing novel OPs with better bio-selectivity.