What you carry at this position in your DNA and what research says about it.
Cardiovascular Health: 5/10 evidence, 42 publications.
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Sample genotype (not yours): A/A
Optimal Enzyme Activity and Lower Cardiovascular Risk
Two copies of the A allele encode the highly stable leucine form of the PON1 enzyme. This results in optimal paraoxonase 1 levels, providing robust antioxidant protection for blood vessels.
What this genotype means: Optimal paraoxonase 1 levels; Enhanced protection against LDL oxidation; Lower risk of coronary artery disease.
Sample genotype (not yours): A/T
Intermediate Enzyme Activity and Typical Risk
Carrying one copy of each allele results in intermediate levels of the PON1 enzyme. This provides a typical level of antioxidant protection with average cardiovascular risk.
What this genotype means: Intermediate paraoxonase 1 levels; Typical antioxidant protection; Average cardiovascular risk profile.
Sample genotype (not yours): T/T
Reduced Enzyme Activity and Higher Cardiovascular Risk
Two copies of the T allele encode the less stable methionine form of the PON1 enzyme. This leads to lower enzyme levels, reducing antioxidant protection for blood vessels.
What this genotype means: Reduced paraoxonase 1 levels; Decreased protection against LDL oxidation; Increased susceptibility to coronary artery disease.
Gene function and biological role
Gene Function: The PON1 gene encodes paraoxonase 1, a calcium-dependent enzyme synthesized primarily in the liver and carried in the blood by high-density lipoprotein particles [1]. This enzyme plays a vital role in protecting both high-density and low-density lipoproteins from oxidative damage [1]. By preventing lipid peroxidation, paraoxonase 1 helps inhibit the inflammatory processes that lead to plaque buildup in the arteries [1]. It also assists in breaking down harmful organophosphates, such as certain pesticides and neurotoxins [2]. Variations in this gene can significantly alter the concentration and protective efficiency of the enzyme in circulation [2].
Variant Impact: The rs854560 variant, commonly known as L55M, is a missense mutation in the PON1 gene that substitutes the amino acid leucine with methionine at position 55 of the protein chain [2]. This specific structural change directly impacts the physical stability of the paraoxonase 1 protein, making the methionine-containing version more prone to degradation [2]. Consequently, individuals carrying the variant allele exhibit significantly lower levels of the enzyme in their blood [2]. This reduction in circulating enzyme levels compromises the body's natural antioxidant defense against LDL oxidation [2]. Over time, lower enzyme activity is associated with an increased susceptibility to early atherosclerosis and coronary artery disease [3].
Key Insight: The L55M variant does not change how the enzyme works, but rather how long it lasts, as the methionine variant degrades much faster in the bloodstream.
Location: PON1. Chromosome 7 · 7q21.3 · 95.3 Mb
Estimated prevalence by population
Global 51.8%; European 40.2%; African 68.1%; East Asian 92.9%; South Asian 63.7%; Americas 52.9%; Ashkenazi 36.3%; Finnish 42.2%; Middle Eastern 32.6%; Amish 42.9%.
Estimated AA genotype frequency.
Global 39.0%; European 46.4%; African 28.8%; East Asian 6.9%; South Asian 32.2%; Americas 39.7%; Ashkenazi 47.9%; Finnish 45.5%; Middle Eastern 49.0%; Amish 45.2%.
Estimated AT genotype frequency.
Global 9.2%; European 13.4%; African 3.1%; East Asian 0.1%; South Asian 4.1%; Americas 7.5%; Ashkenazi 15.8%; Finnish 12.3%; Middle Eastern 18.4%; Amish 11.9%.
Estimated TT genotype frequency.
Showing effects for A/A genotype
Cardiovascular & Metabolic
Heart Disease
Cardiovascular Risk. Evidence: 4/10. Source: PMID 9011577. Lower Risk.
Lipids & Cholesterol
Paraoxonase Activity. Evidence: 3/10. Source: PMID 12525679. Optimal Activity.
Organ Systems
Vision & Eye Health
Diabetic Retinopathy. Evidence: 3/10. Source: PMID 9661650. Lower Risk.
Skin & Hair Conditions
Atopic Eczema. Evidence: 5/10. Source: PMID 32439431. Higher Risk.
Showing effects for A/T genotype
Cardiovascular Risk. Evidence: 4/10. Source: PMID 9011577. Typical Risk.
Paraoxonase Activity. Evidence: 3/10. Source: PMID 12525679. Intermediate.
Diabetic Retinopathy. Evidence: 3/10. Source: PMID 9661650. Typical Risk.
Atopic Eczema. Evidence: 5/10. Source: PMID 32439431. Typical Risk.
Showing effects for T/T genotype
Cardiovascular Risk. Evidence: 4/10. Source: PMID 9011577. Higher Risk.
Paraoxonase Activity. Evidence: 3/10. Source: PMID 12525679. Reduced Activity.
Diabetic Retinopathy. Evidence: 3/10. Source: PMID 9661650. Higher Risk.
Atopic Eczema. Evidence: 5/10. Source: PMID 32439431. Lower Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Having the A/A genotype means the body produces the highly stable leucine variant of the paraoxonase 1 enzyme [1]. This optimal stability translates to higher circulating levels and greater overall activity of the enzyme in the bloodstream [1]. Higher enzyme activity is highly beneficial for cardiovascular health, as it actively prevents the oxidation of LDL cholesterol, a key step in plaque formation [2]. Clinical studies have linked this genotype to a lower risk of developing coronary artery disease and early atherosclerosis [2]. Additionally, individuals with this genotype show better insulin sensitivity and a lower risk of diabetic complications like retinopathy [3]. While some research suggests a slightly higher susceptibility to atopic eczema, the overall cardiovascular benefits remain highly protective [4].
Optimal paraoxonase 1 levels; Enhanced protection against LDL oxidation; Lower risk of coronary artery disease.
Sample genotype: AT (Heterozygous)
This heterozygous genotype results in the production of both the stable leucine and the less stable methionine forms of the paraoxonase 1 enzyme [1]. Consequently, circulating levels and activity of the enzyme are intermediate compared to the homozygotes [1]. This level of enzyme activity generally provides adequate, typical antioxidant protection for blood vessels under normal conditions [2]. Most clinical studies show that individuals with this genotype do not have a significantly elevated risk of cardiovascular disease or diabetic complications [2]. However, maintaining a healthy lifestyle is still important to support overall vascular health [3]. The intermediate enzyme levels also mean typical processing of certain environmental toxins and pesticides [1].
Intermediate paraoxonase 1 levels; Typical antioxidant protection; Average cardiovascular risk profile.
Sample genotype: TT (Homozygous)
Carrying the T/T genotype means the body exclusively produces the less stable methionine variant of the paraoxonase 1 enzyme [1]. This structural instability leads to significantly lower levels and reduced activity of the enzyme in the bloodstream [1]. With less active enzyme available to protect high-density and low-density lipoproteins from oxidation, the risk of arterial plaque buildup increases [2]. Clinical research has associated this genotype with a higher susceptibility to coronary artery disease, particularly in individuals exposed to oxidative stressors like cigarette smoke [2]. It is also linked to an increased risk of microvascular complications in diabetes, such as diabetic retinopathy [3]. Conversely, some studies have noted a lower risk of certain epithelial cancers, though the primary health impact remains cardiovascular [4].
Reduced paraoxonase 1 levels; Decreased protection against LDL oxidation; Increased susceptibility to coronary artery disease.
Variants with shared genetic architecture
rs662 · PON1 Gene · Chr 7 · Heart Disease Risk
rs854572 · PON1 Gene · Chr 7 · Antioxidant Protection
rs705379 · PON1 Gene · Chr 7 · Paraoxonase Enzyme Activity
Impact of inflammation, gene variants, and cigarette smoking on coronary artery disease risk.
A variant of paraoxonase (PON1) gene is associated with diabetic retinopathy in IDDM.
Polygenic risk score for atopic dermatitis in the Canadian population.
Content updated August 2026.
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