There is now good evidence that the antioxidant enzyme paraoxonase-1 (PON-1), which is associated with high density lipoprotein (HDL), exerts an anti-atherogenic effect by protecting low density lipoprotein (LDL) from oxidation. HDL has a well-established inverse relationship with the risk of atherosclerosis [1,2]. HDL is required for the reverse transport of cholesterol from peripheral fibroblasts to the liver, but is also thought to protect LDL from oxidative modification, a key event in the initiation and acceleration of atherosclerosis [3,4]. The antioxidant role of HDL has been attributed to HDL-bound PON-1[5,6]. Paraoxonase (aryldialkylphosphatase EC, PON-1) is a calcium-dependant esterase that circulates in plasma associated bound to HDL [5,6]. It was originally identified by its activity in the metabolism of organophosphates [7,8] such as paraoxon, diazoxon, serin and soman, in addition to arylesters such as phenyl acetate [8]. It thus serves to neutralise anti-cholinesterase nerve gases and insecticides in the body [9]. PON-1 is synthesised in the liver and hence serum levels decrease in chronic liver disease [8]. Recent studies have confirmed that PON-1 is an oxidant-sensitive enzyme that inhibits the atherogenic oxidation of LDL [7]. Low PON-1 activity has been associated with a number of risk factors for coronary heart disease, including diabetes, hypercholesterolaemia and smoking [7]. It is well known, for example, that chronic renal failure results in accelerated atherosclerosis and studies have shown that haemodialysis increases production of reactive oxygen species while decreasing PON-1 activity [7,8]. There are also correlations between PON-1 enzyme levels and plasma lipids; PON-1 activity is lowered in familial hypercholesterolaemia, insulin dependent diabetes and amongst survivors of myocardial infarction [9]. PON-1 is an enzyme with three activities: paraoxonase, arylesterase and dyazoxonase [10]. Paraoxonase thus hydrolyses The paraoxonase and arylesterase activities of PON-1 both decrease in hypercholesterolaemia [10]. Pharmacologic therapy with simvastatin has been reported to increase serum PON-1 activity [6]. Pomegranate juice consumption or the intake of vitamin C and E supplements are also reported to raise enzyme levels [6].

Patient Instructions:

No special patient preparation is required prior to venipuncture.

Clinical Indications:

Serum paraoxonase (PON-1) is an antioxidant enzyme whose activity is associated with a decreased atherosclerosis risk; its measurement may therefore give useful information as to a subject’s cardiovascular risk. Since PON-1 is induced in oxidative stress, careful assessment of its serum activity is indicative of the subject’s ability to metabolise organophosphates and other xenobiotics.

Included in Profiles:

Included in Biolab Antioxidant Profile


Sample Requirements:

Green (lithium heparin)/Gold (SST) - Serum or plasma is suitable for paraoxonase measurement. The specimen of choice is whole blood, collected with heparin as an anticoagulant. However, the enzyme is calcium-dependent, so blood collected into other anti-coagulants such as EDTA is unsuitable for assay.

Postal Samples:


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