Biotransformation of methyl parathion by human foetal liver glutathione S-transferases: an in vitro study

1. The role of human foetal liver glutathione S-transferases in the detoxification of methyl parathion was investigated.2. Glutathione S-transferases were partially purified by affinity chromatography utilizing reduced glutathione as the ligand coupled to epoxy-activated Sepharose 4B. This resulted in the isolation of material with an average activity (mean ± S.E.) of 58.90 ± 4.83 µmol 1 -chloro-2,4-dinitrobenzenceo njugate formed/min per mg. representing a purification of 70-fold.3. These partially purified foetal liver transferases catalysed the metabolism of methyl parathion exclusively to desmethyl parathion via O-dealkylation.4. High-performance liquid Chromatography, radiometric analysis of the enzymic reaction, and co-chromatography with reference standard on thin-layer chromatography confirmed the sole metabolite as desmethyl parathion.5. The range of foetal liver activity towards methyl parathion was from 30 to 122 nmol desmethyl parathion formed/min per mg.6. Analysis of the kinetic parameters o...