TPMT
Thiopurine S-methyltransferase
Gene Number: 7172
Location: 6p22.3
Key Functions: Thiopurine metabolism, drug detoxification, TPMT enzymatic activity
TPMT encodes thiopurine S-methyltransferase, an enzyme that metabolizes thiopurine drugs such as azathioprine, 6-mercaptopurine, and thioguanine. TPMT methylates these compounds, helping to prevent accumulation of toxic metabolites in the body.
Genetic variants in TPMT can lead to reduced enzyme activity, increasing the risk of severe bone marrow suppression when standard doses of thiopurines are used. Testing for TPMT function is essential before initiating thiopurine therapy.
SNP ID | Your Genotype | Alternative Alleles | Interpretation |
|---|---|---|---|
rs1800460 | No matching variant or no valid DNA data | T | No interpretation available |
rs1142345 | No matching variant or no valid DNA data | C | No interpretation available |
rs1800460
CC – Normal TPMT activity; standard metabolizer (R).
TC – Reduced TPMT activity; impaired thiopurine metabolism (R).
TT – Reduced TPMT activity; impaired thiopurine metabolism (R).
Functional effect: The T allele (TPMT3B / part of 3A when combined with rs1142345 C) dramatically reduces enzyme function, increasing the risk of treatment-induced toxicity (R).
rs1142345
TT –Normal TPMT activity; standard thiopurine metabolism (R).
TC – Intermediate TPMT activity; moderate metabolism impairment (R).
CC –Very low TPMT activity; high risk of thiopurine drug toxicity (R).
Functional effect: The C allele causes marked reduction in TPMT enzyme levels, leading to drug accumulation and potential myelosuppression [R].
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