Lipoproteins and hydrolysis of organophosphorus compounds

Paraoxonase of human and animal sera was shown to be a structural part of high density lipoproteins (HDL) by immunoprecipitation, heparin- or polyethyleneglycol fractionation, ultracentrifugation and gel chromatography. Frequency distribution of paraoxonase activity in human sera is trimodal. Human individuals, with respect to paraoxon detoxication, can be distinguished into low and high detoxicators using ratios of phenylacetate and paraoxon hydrolysis as well as activation with ethanolamine and sodium chloride. With conversion of alpha-lipoprotein subtype HDL3 to HDL2, specific activities of paraoxonase and arylesterase are increasing about 3.5-fold in low detoxicator individuals and 1.9-fold in high detoxicators, indicating that more than 90% of HDL2 particle-bound paraoxonase and arylesterase activity are incorporated during the HDL conversion process. HDL cholesterol concentrations in individual sera were shown to be positively correlated to both serum paraoxonase and arylesterase activities.