Relationships between paraoxon and 2-coumaranone hydrolytic activities in sera genotyped for PON1 Q192R polymorphism

Objectives: To set-up a method for a direct evaluation in human serum of paraoxonase enzymatic activities, establishing a possible correlation with Q192R genotype polymorphism. Design and methods: 101 different human serum samples were genotyped for paraoxonase Q192R polymorphism by PCR restriction analysis, and evaluated spectrophotometrically with regard to paraoxon and 2-coumaranone hydrolytic activities. Both activities of paraoxonase were assayed, quantified through normalization by arylesterase activity, and compared with the data concerning Q/R genetic polymorphism. Results: The mean normalized paraoxonase activity was found to be significantly higher in RR than in QQ human sera (3.99 +/- 0.6 versus 1.32 +/- 0.44; P < 0.0001); instead, the 2-coumaranone hydrolysis showed an opposite trend (0.10 +/- 0.02 versus 0.23 +/- 0.04, in RR and QQ sera respectively; P < 0.0001). Conclusions: These methods were successfully applied to the whole serum, suggesting a possible use of this approach for a clinically relevant phenotypic characterization. (C) 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.