Lo J F, Wang H F, Tam M F, Lee T C
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China.
Biochem J. 1992 Dec 15;288 ( Pt 3)(Pt 3):977-82. doi: 10.1042/bj2880977.
A glutathione S-transferase (GST) was purified from an arsenic-resistant Chinese hamster ovary cell line, SA7. The SA7 GST was shown to catalyse the conjugation of glutathione and ethacrynic acid, a specific substrate for Pi class GST. Its N-terminal amino-acid sequence has 80% identical residues to that of rat GST P and human GST pi. Thus, the GST purified from SA7 cells belongs to the Pi family. Treatment with Cibacron Blue or ethacrynic acid, which are GST inhibitors, significantly decreased the resistance of SA7 cells to sodium arsenite. On the other hand, pretreatment of SA7N cells, a partial revertant of SA7 cells, with sublethal doses of sodium arsenite, cadmium acetate or zinc sulphate resulted in re-elevation of GST activities and the cells regained the arsenic resistance. The regained arsenic resistance was well correlated with the levels of GST pi which were induced dose-dependently by zinc sulphate. Heat-shock treatment (45 degrees C for 10 min) did not increase GST pi expression or arsenic resistance of SA7N cells. The results indicate that GST pi is possibly involved in the mechanism of arsenic detoxification.
从抗砷的中国仓鼠卵巢细胞系SA7中纯化出一种谷胱甘肽S-转移酶（GST）。SA7 GST被证明能催化谷胱甘肽与依他尼酸（Pi类GST的一种特异性底物）的结合。其N端氨基酸序列与大鼠GST P和人GST pi的N端氨基酸序列有80%的相同残基。因此，从SA7细胞中纯化出的GST属于Pi家族。用GST抑制剂汽巴蓝或依他尼酸处理显著降低了SA7细胞对亚砷酸钠的抗性。另一方面，用亚致死剂量的亚砷酸钠、醋酸镉或硫酸锌预处理SA7细胞的部分回复株SA7N细胞，导致GST活性再次升高，细胞恢复了对砷的抗性。恢复的抗砷性与硫酸锌剂量依赖性诱导的GST pi水平密切相关。热休克处理（45℃处理10分钟）并未增加SA7N细胞中GST pi的表达或抗砷性。结果表明，GST pi可能参与了砷解毒机制。
