Department of Clinical Biochemistry, Faculty of Pharmacy, Askerceva 7, SI-1000, University of Ljubljana, Ljubljana, Slovenia.
Biochem Pharmacol. 2012 Apr 1;83(7):969-76. doi: 10.1016/j.bcp.2012.01.010. Epub 2012 Jan 17.
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 TPMT1 and variant *3C allozymes. In addition to TPMT genotyping, SAM may serve as an important biochemical marker in individualization of thiopurine therapy.
硫嘌呤甲基转移酶（TPMT；EC 2.1.1.67）在硫嘌呤治疗结果中起着关键作用。然而，关于其细胞内调节的了解甚少。在这里，我们描述了生理水平的 S-腺苷-L-甲硫氨酸（SAM）和相关代谢物波动对细胞系和健康供体红细胞中 TPMT 活性水平的影响。我们确定了高 SAM 浓度（n=96）的野生型 TPMT1/1 个体中的 TPMT 活性更高，而低 SAM 水平组（n=19；P<0.001）。这些发现证实了我们的体外研究结果，即细胞生长培养基中 L-蛋氨酸（Met）的限制可可逆地降低 TPMT 活性和蛋白水平。选择性抑制 Met 代谢的不同成分表明，SAM 是直接翻译后 TPMT 稳定的隐含因素。在野生型 TPMT1 和变体3C 同种型的情况下，SAM 介导的 TPMT 稳定的效果最大。除了 TPMT 基因分型外，SAM 还可以作为硫嘌呤治疗个体化的重要生化标志物。
