In vitro effects of some pesticides on pon1q192 and pon1r192 isoenzymes from human serum

Abstract

Human serum paraoxonase 1 (PON1) contains two polymorphic forms, Q (glutamine) or R (arginine) located at codon 192. The Q isoform has a higher activity for hydrolysis of diazoxon, sarin, and soman; whereas the R isoform has a higher activity for hydrolysis of paraoxon and chlorpyrifos oxon. In this study, the in vitro effects of commonly used pesticides (Purtapyr, Roundup, Agrofarm and Practicur) on purified human serum Q and R isoenzymes were investigated. Q and R isoforms were separately purified with ammonium sulphate precipitation and hydrophobic interaction chromatography, and the in vitro effects of the pesticides on purifying Q and R were determined using paraoxon as a substrate. IC50 values of these pesticides ex-hibiting inhibition effects were found from graphs of paraoxonase activity percentage by plotting their concentrations. The inhibition kinetics (Ki) interaction of these pesticides with the human serum Q and R isoenzymes were also determined.