Thiopurine Methyltransferase in Thai Population

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Pompen Pramyothin
Parinda Peradhamanon


The cytosolic enzyme, thiopurine methyltransferase (TPMT) catalyzes the S-methylation of aromatic and heterocyclic sulfhydryl compounds such as 6-mercaptopurine. Genetic regulation of TPMT activity is associated with large interindividual variations in thiopurine toxicity and efficacy. Assessment of TPMP genotype/phenotype will increase rational outcome of individual drug therapy. In the present investigation, TPMT activity was measured by the radiochemical assay from blood samples of 539 randomly selected Thai subjects. The genetic polymorphism of TPMT was trimodal distribution, TPMT activity ranged from 0 - 23.5 Units/ml RBC with the average of 6.91 ± 3.68 Units/ml RBC. Most of the Thai subjects were intermediate metabolizers (95.35 %), followed by high (3.75 %) and low (0.93%) metabolizers. Gender, blood groups and smoking had no effect on TPMT activity.

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