NAT2 rs1799931: Understanding the 857G>A Variant
The NAT2 rs1799931 variant, also known as 857G>A, is a genetic change in the NAT2 gene that influences how the body processes certain medications. It is a key marker used to identify individuals who may have a 'slow acetylator' phenotype, which can affect how they respond to specific drugs.
What each genotype means
Normal enzyme activity
This genotype is associated with the rapid or intermediate acetylator phenotype, which is the standard metabolic activity for the NAT2 enzyme. Individuals with this genotype typically process medications like isoniazid at a standard rate. Please discuss your medication dosing and any potential side effects with your clinician or pharmacist.
This is the most common genotype in most global populations, though it is less frequent in East Asian populations where the A allele is more prevalent.
Reduced enzyme activity
Carrying one copy of the A allele is associated with a reduced capacity to metabolize certain drugs, often categorized as an intermediate acetylator phenotype. This variant is a defining mutation of the NAT2*7 allele, which is linked to slower drug processing. Please consult your healthcare provider or pharmacist regarding how this may influence your response to specific medications.
This genotype is found in approximately 10-25% of individuals in East Asian populations and is significantly less common in European populations.
Slow enzyme activity
This genotype is associated with a slow acetylator phenotype, meaning your body may process certain medications more slowly than average. This can lead to higher drug concentrations in the blood, which may increase the risk of side effects for drugs metabolized by NAT2. Always discuss your medication management and potential dosing adjustments with your clinician or pharmacist.
This genotype is most prevalent in East Asian populations and is rare in individuals of European ancestry.
What is the rs1799931 Variant?
The variant rs1799931, often referred to as 857G>A, is a single nucleotide polymorphism (SNP) located within the NAT2 gene. In genetics, a SNP represents a variation at a single position in the DNA sequence. This specific change involves the substitution of the nucleotide guanine (G) with adenine (A) at position 857. This alteration results in a change in the protein structure, specifically replacing the amino acid glycine with glutamic acid at position 286 (p.Gly286Glu). Because this change can alter the function of the resulting enzyme, it is a subject of significant interest in the field of pharmacogenomics, which studies how an individual's genetic makeup influences their response to drugs.
The Role of the NAT2 Gene
The NAT2 gene provides instructions for making an enzyme called N-acetyltransferase 2. This enzyme is primarily responsible for the 'acetylation' of various drugs and environmental toxins, a process that helps the body break down and eliminate these substances. The speed at which this enzyme functions varies among individuals, leading to classifications such as 'rapid,' 'intermediate,' or 'slow' acetylators. The rs1799931 variant is one of several genetic markers that contribute to the slow acetylator phenotype. When an individual carries this variant, the NAT2 enzyme may have reduced activity, potentially leading to slower clearance of certain medications from the bloodstream. This is particularly relevant for drugs like isoniazid, which is used to treat tuberculosis.
Research and Clinical Associations
Research has linked the rs1799931 variant to the slow acetylator phenotype, though the impact can be substrate-dependent, meaning it may affect the metabolism of some drugs more than others. In clinical settings, identifying an individual's NAT2 status is important because slow acetylators may be at a higher risk for drug-induced side effects, such as liver injury, when taking certain medications. However, the evidence strength for this specific variant's clinical impact is considered limited in some contexts, and findings can vary based on the specific drug being studied. It is essential to understand that genetic associations are statistical observations across populations and do not predict an individual's specific clinical outcome. Always consult with a healthcare provider or pharmacist to discuss how your genetic profile might influence your medication management.
Population Frequency
The frequency of the rs1799931 variant varies significantly across different ancestral groups. It is most prevalent in East Asian populations, where the minor allele frequency is approximately 10-15%. In contrast, the variant is much less common in European populations, where it is found at a frequency of less than 1%. Understanding these population-specific differences is a key component of pharmacogenomic research, as it helps clinicians anticipate the prevalence of certain metabolic phenotypes within different communities.
What You Can Do With This Information
Knowing your genotype for rs1799931 can be a useful piece of information to share with your doctor or pharmacist, especially if you are prescribed medications known to be metabolized by the NAT2 enzyme. This information does not serve as a medical diagnosis, nor should it be used to make independent decisions about your health or medication dosing. If you have concerns about how your body processes a specific drug, the best course of action is to have a conversation with your healthcare provider. They can interpret your genetic information in the context of your overall health, medical history, and current treatment plan to ensure the safest and most effective care.
How common is this variant?
The rs1799931 variant has a minor allele frequency of approximately 10-15% in East Asian populations and less than 1% in European populations.
Frequently asked questions
Does having the rs1799931 variant mean I am a slow acetylator?
The rs1799931 variant is one of several markers that contribute to the slow acetylator phenotype. While it is a significant indicator, an individual's overall acetylation status is determined by the combination of all their NAT2 variants.
Can I use this information to change my medication dose?
No. You should never change your medication dosage based on genetic information alone. Always consult your doctor or pharmacist before making any changes to your prescribed treatment.
Is rs1799931 the same as NAT2*7?
Yes, the rs1799931 variant is the defining mutation for the NAT2*7 allele. This allele is commonly associated with the slow acetylator phenotype.
Why is this variant more common in some populations?
Genetic variants often vary in frequency across populations due to historical migration patterns, natural selection, and genetic drift. The higher frequency of rs1799931 in East Asian populations is a well-documented example of this genetic diversity.
Sources & further reading
Educational information only, last refreshed 10/9/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Coding variant c.857G>A (p.Gly286Glu) defining the NAT2*14 allele (often associated with slow acetylation).
Coding variant c.481C>T (p.Leu161Leu) serving as a diagnostic marker for several NAT2 slow acetylator haplotypes, including *5.
Missense variant (590G>A) defining the NAT2*6A allele, associated with slow acetylator phenotype.
Synonymous variant (282C>T) associated with the NAT2*6 allele, contributing to slow acetylator status.
This variant (c.590G>A, p.Arg197Gln) is a well-characterized slow acetylator allele in the NAT2 gene, influencing the metabolism of drugs like isoniazid.
Tag SNP defining the rapid versus slow N-acetyltransferase 2 acetylator phenotype, showing substantial allele frequency divergence across world ancestries.