[The role of esterases in the toxicity of organothiophosphorus insectoacaricides containing a fragment of mercaptoacetic acid].

Interaction of insectoacaricide Me (EtO)P(S)SCH2SCH2COOMe (I), its activation metabolites (P = O (II), S = O, and P = O, S = O (III) analogues), and a detoxication product (-COOH analoque (IV) with rat liver carboxylesterase, acetylcholinesterase and butyrylcholinesterase of warm-blooded animals, as well as with cholinesterase and carboxylesterase of American cockroach has been studied. Low toxicity of (I) towards warm-blooded animals and American cockroach is shown to result from its rapid hydrolysis with corresponding carboxylesterases to form (IV). Monothiophosphonates (II) and (III) are not hydrolyzed by carboxylesterases but inhibit them irreversibly. High toxicity of (I) towards aphids can be ascribed to low activity of the carboxylesterase of that insect.