Methods for Measuring Serum Activity Levels of the 192 Q and R Isoenzymes of Paraoxonase 1 in QR Heterozygous Individuals
Open Access
- 1 August 2013
- journal article
- Published by Oxford University Press (OUP) in Clinical Chemistry
- Vol. 59 (8), 1251-1259
- https://doi.org/10.1373/clinchem.2012.199331
Abstract
BACKGROUND: Paraoxonase 1 (PON1), an esterase that hydrolyzes toxic organophosphates and has antioxidative and antiatherogenic properties, contains a common polymorphism at position 192: glutamine (Q) or arginine (R). The Q and R isoenzymes exhibit different physical and protective properties. We describe 2 methods for quantifying their serum activity levels. METHODS: We measured serum hydrolytic activity with paraoxon [paraoxonase (PXN) activity], phenylacetate [arylesterase (AE) activity], and diazoxon [diazoxonase (DZN) activity] with standard automated assays. We determined PON1 Q192R genotypes with PCR and Q192R phenotypes using the PXN/AE and PXN/DZN ratios. Interpolation equations were empirically derived to predict the percentage of total PON1 hydrolytic activity due to the Q isoenzyme (%Q) from the PXN/AE and PXN/DZN ratios; %R is 100 − %Q. We estimated Q and R isoenzyme activity levels in sera from 2095 veterans by multiplying AE activity, a measure of total PON1 hydrolytic activity, by %Q and %R. RESULTS: In all 2095 samples, the PXN/AE and PXN/DZN ratios predicted Q192R phenotypes with nearly identical accuracy (κ = 0.997). In the 925 QR heterozygotes, the 2 interpolation methods predicted Q and R isoenzyme activity levels with excellent agreement (intraclass correlation 0.94). After excluding a few genotype/phenotype-discordant samples, the percentage of total PON1 activity due to the Q isoenzyme ranged from 22% to 70%. CONCLUSIONS: These new interpolation methods allow accurate estimation of PON1 192 Q and R isoenzyme activity levels, increasing specificity and power for studying susceptibility to disease.Keywords
Funding Information
- American Heart Association (0635075N, DAMD17-01-1-0741)
- U.S. Army Medical Research and Materiel Commanda
- Dallas VA Medical Center (VA549-P-0027)
This publication has 23 references indexed in Scilit:
- Association of Organophosphate Pesticide Exposure and Paraoxonase with Birth Outcome in Mexican-American WomenPLOS ONE, 2011
- Prenatal Exposure to Organophosphates, Paraoxonase 1, and Cognitive Development in ChildhoodEnvironmental Health Perspectives, 2011
- Serum Cholinesterase Inhibition in Relation to Paraoxonase-1 (PON1) Status among Organophosphate-Exposed Agricultural Pesticide HandlersEnvironmental Health Perspectives, 2009
- Paraoxonases role in the prevention of cardiovascular diseasesBioFactors, 2009
- Human paraoxonases (PON1, PON2, and PON3) are lactonases with overlapping and distinct substrate specificitiesJournal of Lipid Research, 2005
- Paraoxonase-1 does not reduce or modify oxidation of phospholipids by peroxynitriteFree Radical Biology & Medicine, 2005
- Role of Paraoxonase (PON1) Status in Pesticide Sensitivity: Genetic and Temporal DeterminantsNeuroToxicology, 2004
- In utero pesticide exposure, maternal paraoxonase activity, and head circumference.Environmental Health Perspectives, 2004
- Pharmacogenetics of paraoxonases: a brief reviewNaunyn-Schmiedebergs Archiv für experimentelle Pathologie und Pharmakologie, 2004
- Functional Genomics of the Paraoxonase (PON1) Polymorphisms: Effects on Pesticide Sensitivity, Cardiovascular Disease, and Drug MetabolismAnnual Review of Medicine, 2003