Methods for measuring serum activity levels of the 192 Q and R isoenzymes of paraoxonase 1 in QR heterozygous individuals

John F. Teiber, Gerald L. Kramer, Robert W. Haley

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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). TheQand 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.WedeterminedPON1Q192Rgenotypes withPCRand 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 theQ isoenzyme (%Q) from the PXN/AE and PXN/DZN ratios; %R is 100%Q. We estimatedQand R isoenzyme activity levels in sera from 2095 veterans by multiplying AE activity, a measure of total PON1 hydrolytic activity, by%Qand %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 925QRheterozygotes, 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.

Original languageEnglish (US)
Pages (from-to)1251-1259
Number of pages9
JournalClinical chemistry
Issue number8
StatePublished - Aug 2013

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical


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