THIOPURINE METHYLTRANSFERASE ACTIVITY IN A KOREAN POPULATION-SAMPLE OF CHILDREN

Thiopurine methyltransferase (TPMT) is a cytoplasmic enzyme that catal yzes the S-methylation of the cytotoxic drugs 6-mercaytopurine and aza thioprine. Red blood cell (RBC) TPMT activity is subject to genetic po lymorphism, and we have previously demonstrated an interethnic differe nce in TPMT activity, To investigate whether there was a race-related difference in RBC TPMT activity, TPMT was measured in a Korean populat ion sample of 309 healthy children, Mean TPMT activity in healthy Kore an children was 12.4 +/- 2,4 units/ml RBC, which is similar to the ear lier reported TPMT activities in white populations, In contrast to thr bimodal or trimodal frequency distributions of RBC TPMT activity in m ost other population samples, the frequency distribution histogram, th e probit plot, and the Shapiro-Wilk test supported a normal distributi on of TPMT activity in this Korean population sample of healthy childr en, Mean RBC TPMT activity showed a tendency to decrease with age, but it was not statistically significant. No gender-related difference in RBC TPMT activity was found.