In vitro transformation of dithiopyr by rat liver enzymes: conversion of methylthioesters to acids by oxygenases.

1. Transformation of dithiopyr by rat liver enzymes in vitro produced the corresponding monoacids as the predominant metabolites. 2. Transformations of the methylthioester functional groups in dithiopyr to the monoacids were mediated via rat liver microsomal oxygenases, and not via esterases. 3. Based on the formation of a dithiopyr-glutathione conjugate, the mechanism of monoacid formation is believed to proceed through an initial sulphur oxidation of the methylthioester group and a subsequent nucleophilic displacement reaction.