Higher frequency of the galactose-1-phosphate uridyl transferase gene K285N mutation in the Slovenian population.

OBJECTIVES: To analyze a healthy Slovenian population for the frequency of the classical galactosemia allele K285N. DESIGN AND METHODS: DNA was analyzed by means of polymerase chain reaction and restriction fragment length polymorphism. RESULTS: The allele frequency of the K285N mutation in Slovenian population is 0.29%. CONCLUSIONS: The allele frequency of the K285N mutation in Slovenian population is higher than in other Caucasian populations. K285N is one of the most frequent classical galactosemia mutations in the Slovenian population.

Post-translational stabilization of thiopurine S-methyltransferase by S-adenosyl-L-methionine reveals regulation of TPMT*1 and *3C allozymes.

Thiopurine S-methyltransferase (TPMT; EC 2.1.1.67) plays a pivotal role in thiopurine treatment outcomes. However, little has been known about its intracellular regulation. Here, we describe the effect of fluctuations in physiological levels of S-adenosyl-L-methionine (SAM) and related metabolites on TPMT activity levels in cell lines and erythrocytes from healthy donors. We determined higher TPMT activity in wild-type TPMT*1/*1 individuals with high SAM concentrations (n=96) compared to the low SAM level group (n=19; P<0.001). These findings confirm the results of our in vitro studies, which demonstrated that the restriction of L-methionine (Met) in cell growth media reversibly decreased TPMT activity and protein levels. Selective inhibition of distinct components of Met metabolism was used to demonstrate that SAM is implicitly responsible for direct post-translational TPMT stabilization. The greatest effect of SAM-mediated TPMT stabilization was observed in the case of wild-type TPMT*1 and variant *3C allozymes. In addition to TPMT genotyping, SAM may serve as an important biochemical marker in individualization of thiopurine therapy.