Department of Internal Medicine, Division of Epidemiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-8874, USA.
Clin Chem. 2013 Aug;59(8):1251-9. doi: 10.1373/clinchem.2012.199331.
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.
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.
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%.
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.
对氧磷酶 1（PON1）是一种酯酶，可水解有毒的有机磷酸酯，具有抗氧化和抗动脉粥样硬化特性，其 192 位含有一个常见的多态性：谷氨酸（Q）或精氨酸（R）。Q 和 R 同工酶表现出不同的物理和保护特性。我们描述了 2 种定量测定其血清活性水平的方法。
我们使用标准自动化测定法测量了对氧磷（PON）活性、苯乙酸酯（AE）活性和苯二甲酸二辛酯（DZN）活性的血清水解活性。我们使用 PCR 测定了 PON1 Q192R 基因型，并使用 PXN/AE 和 PXN/DZN 比值测定了 PON1 Q192R 表型。我们通过经验推导了插值方程，从 PXN/AE 和 PXN/DZN 比值预测 Q 同工酶占总 PON1 水解活性的百分比（%Q）；%R 是 100-%Q。我们通过将 AE 活性（总 PON1 水解活性的衡量标准）乘以%Q 和%R，估计了 2095 名退伍军人血清中的 Q 和 R 同工酶活性水平。
在所有 2095 个样本中，PXN/AE 和 PXN/DZN 比值对 Q192R 表型的预测准确率几乎相同（κ=0.997）。在 925 个 QR 杂合子中，2 种插值方法对 Q 和 R 同工酶活性水平的预测具有极好的一致性（组内相关系数 0.94）。排除少数基因型/表型不一致的样本后，Q 同工酶占总 PON1 活性的百分比范围为 22%-70%。
这些新的插值方法可以准确估计 PON1 192 Q 和 R 同工酶的活性水平，提高了研究疾病易感性的特异性和效能。
