Inhibition of Beef Liver Hydrolytic Enzymes by Organophosphorus Pesticides

Abstract

The effect of several organic solvents on the rate at which the carboxylesterases of beef liver hydrolyze u-nitrophenylbutyrate is reported. The organic solvents studied were acetone, methanol, ethanol, «propanol, 2-propanol, glycerol, dimethyl sulfoxide (DMSO), «-butanol, rec-butanol, rcrt-butanol, isobutanol, and «-pentanol. These solvents also affected the inhibition of liver enzymes by the pesticide Ruelene. A preliminary study of these effects was carried out at the 2.5% solvent concentration. This was followed by a more detailed study on acetone, methanol, glycerol, and DMSO at concentrations of up to 20%. The organic solvents were classified according to their effects on enzyme activation and inhibition: those which activated and decreased inhibition, those which deactivated and decreased inhibition, those which activated and increased inhibition, and those which deactivated and increased inhibition. The concentration of the solvent was a critical factor in enzyme activation and inhibition. The effects of these solvents on the optical properties of the reaction product, -nitrophenol, were also studied.

Liver esterases of rhesus monkey: inhibition and activation by selected pesticides

“…With tepa, consistent activation was observed only when this pesticide was in 5 /d of methanol, indicating that the amount of methanol might have influenced the enzyme activation. This observation concurred with the previous reports (Villeneuve et al, 1969;Mendoza and Hatina, 1970) that solvents could affect the activity of the enzyme. The relation of activation to the pesticide concentration was not linear, but carefully controlled experiments confirmed that activation was consistent only when methyl parathion and tepa were present at low concentrations.…”