John F Teiber1, Gerald L Kramer, Robert W Haley. 1. Department of Internal Medicine, Division of Epidemiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-8874, USA. john.teiber@utsouthwestern.edu
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.
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 PON1Q192R 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.
Authors: Htet W Khine; John F Teiber; Robert W Haley; Amit Khera; Colby R Ayers; Anand Rohatgi Journal: Atherosclerosis Date: 2017-06-03 Impact factor: 5.162
Authors: Robert W Haley; Gerald Kramer; Junhui Xiao; Jill A Dever; John F Teiber Journal: Environ Health Perspect Date: 2022-05-11 Impact factor: 11.035