NAT2 rs1208: Acetylation and Drug Metabolism
The single nucleotide polymorphism rs1208 is an exonic missense variant within the NAT2 gene that alters an amino acid in the N-acetyltransferase 2 enzyme. Functionally, it serves as the defining tag for the NAT2*12 allelic series and appears within multi-variant slow-acetylator haplotypes such as NAT2*5B. While rs1208 by itself does not significantly diminish enzyme activity in vitro, its presence across different genomic backgrounds contributes to statistical variations in drug clearance and xenobiotic metabolism.
What each genotype means
Typical baseline NAT2 activity
You carry two copies of the ancestral A allele at rs1208. By itself, this genotype does not alter N-acetyltransferase 2 enzyme function, but overall drug metabolism depends on your broader NAT2 haplotype combining other functional variants. If you are taking medications metabolized by NAT2 such as isoniazid, hydralazine, or sulfamethoxazole, consult your clinician or pharmacist to interpret your complete profile.
Carried by approximately 25% to 45% of individuals globally, though frequency varies considerably across different ancestral backgrounds.
Variant carrier / mixed haplotype
You carry one copy of the G allele (defining the NAT2*12 cluster) alongside one ancestral A allele. While the G allele alone does not decrease NAT2 enzymatic speed, it often co-occurs on complex haplotypes alongside other slow-acetylator mutations. Because overall acetylation status depends on full haplotype phase, discuss any medication dosing or monitoring with your healthcare provider.
Carried by roughly 40% to 50% of people across many global populations.
Homozygous rapid-marker variant
You carry two copies of the G allele at rs1208, which encodes the p.Lys268Arg substitution associated with the rapid-acetylating NAT2*12 allele series. In isolation this substitution retains standard enzymatic activity, though it frequently co-segregates with other slow-activity variants in certain genetic backgrounds. You should review your complete multi-SNP NAT2 status with a doctor or pharmacist before making any changes to prescribed drugs.
Found in approximately 10% to 25% of individuals worldwide, with lower frequencies observed in East Asian populations.
Genetic Architecture and the NAT2 Locus
Located on the short arm of chromosome 8 at 8p22, the N-acetyltransferase 2 (NAT2) gene consists of a single protein-coding exon that produces an enzyme spanning 290 amino acids. The variant rs1208 represents an exonic substitution at nucleotide position 803 (c.803A>G, causing the missense change p.Lys268Arg). In classic pharmacogenetic nomenclature, the wild-type reference allele NAT2*4 carries the 803A allele, whereas the GRCh38 human reference assembly incorporates the 803G allele corresponding to the NAT2*12A sequence. Because the NAT2 coding region contains no introns, several single nucleotide polymorphisms frequently travel together on identical physical chromosomes. Consequently, the biochemical impact of rs1208 depends heavily on which co-inherited variants flank it within the broader haplotype.
Biological Function of N-Acetyltransferase 2
The NAT2 enzyme catalyzes phase II biotransformation by transferring an acetyl group from acetyl-coenzyme A onto arylamine and hydrazine substrates. This process is crucial for clearing therapeutics like isoniazid, sulfamethoxazole, and hydralazine, as well as detoxifying or bioactivating environmental arylamine carcinogens found in tobacco smoke and well-cooked meats. Recombinant expression studies in mammalian cell models indicate that the p.Lys268Arg change introduced by rs1208 does not disrupt mRNA expression, catalytic active sites, or protein stability. Alone, the resulting NAT2*12 enzyme maintains substrate affinity and velocity comparable to the standard NAT2*4 enzyme, categorizing isolated rs1208 G alleles as rapid acetylators.
Clinical Evidence and Phenotype Prediction
The clinical significance of rs1208 is complex because it is found in both rapid and slow metabolizer haplotypes. When rs1208 occurs alongside inactivating missense mutations—such as rs1801280 (341T>C) within the common NAT2*5B haplotype—the overall haplotype causes a slow acetylator phenotype. As an isolated marker, rs1208 predicts true metabolic status with approximately 78% accuracy, which is why clinical pharmacogenomics platforms evaluate multivariant panels. Statistical studies have linked genotypes carrying rs1208 alleles to variable rates of anti-tuberculosis drug-induced hepatotoxicity (ATDH) and bladder cancer risk. However, researchers view these clinical associations as indirect effects driven by linkage disequilibrium with bona fide slow-acetylating variants.
Navigating Pharmacogenomic Information Responsibly
Direct-to-consumer or laboratory-based testing showing your rs1208 genotype provides partial insight into drug processing, but it is not a diagnostic tool or standalone dosing guide. Because NAT2 acetylator status relies on phase resolution of up to seven common polymorphic sites, knowing your rs1208 genotype alone cannot confirm whether you are a rapid, intermediate, or slow metabolizer. Patients taking medications metabolized by NAT2, such as isoniazid or sulfamethoxazole, should never adjust medication regimens based on genetic readouts. Instead, discuss any pharmacogenomic data with your prescribing physician or a clinical pharmacist, who can evaluate your broader haplotype alongside hepatic function, kidney health, and concurrent drug exposures.
How common is this variant?
The minor allele frequency for rs1208 ranges between 0.35 and 0.50 globally, with the G allele occurring at elevated frequencies in European and African populations while displaying lower prevalence in certain East Asian cohorts.
Frequently asked questions
Does my rs1208 genotype mean I am a slow metabolizer?
Not necessarily. Although rs1208 can occur on the same chromosome as slow-metabolizing mutations like NAT2*5B, the rs1208 variant itself produces normal enzyme activity when present alone. Determining your true metabolizer status requires evaluating a broader multi-SNP NAT2 panel.
Can rs1208 predict adverse drug reactions to tuberculosis therapy?
Some retrospective studies show statistical correlations between rs1208 genotypes and isoniazid-induced liver injury, but this association is largely indirect. The risk is primarily driven by linked variants that truly decrease NAT2 enzyme production or function rather than rs1208 itself.
What is the NAT2*12 allele?
NAT2*12 is an allelic designation defined by the presence of the 803G variant at rs1208 in the absence of functional inactivating mutations. In laboratory assays, the NAT2*12 enzyme demonstrates catalytic rates similar to the reference NAT2*4 enzyme, categorizing it as a rapid acetylator allele.
Should I adjust my medication dosage based on rs1208 alone?
No, you should never modify your prescription dosage based solely on rs1208 results. Professional guidelines require multi-variant haplotype assignment to predict metabolic phenotypes, and any dosage modifications must be directed by a licensed healthcare provider.
Sources & further reading
Educational information only, last refreshed 9/11/2026. 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 polymorphism (857G>A) representing the defining mutation of the slow acetylator NAT2*7 allele.
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.