Mojena M, Bosca L, Rider M H, Rousseau G G, Hue L
Hormone and Metabolic Research Unit, Louvain University Medical School, Brussels, Belgium.
Biochem Pharmacol. 1992 Feb 18;43(4):671-8. doi: 10.1016/0006-2952(92)90229-c.
The activity of 6-phosphofructo-2-kinase (PFK-2), the enzyme that catalyses the synthesis of fructose 2,6-bisphosphate (Fru-2,6-P2), was inhibited by mercaptopurines in vitro. Inhibition was observed with the purified enzyme from rat liver and bovine heart, and in extracts from rat lymphocytes and hepatoma cells, chick embryo fibroblasts, and human HeLa and lymphoblastoid cells. Half-maximal effect was obtained with 0.1-0.2 mM mercaptopurine and maximal inhibition ranged between 50 and 90% depending on the enzyme preparation. The inhibition resulted from a decrease in Vmax with no change in Km for ATP. The inhibition was relieved by treatment of the enzyme with thiol reducing agents, suggesting that it involves the formation of a mixed disulfide between mercaptopurine and thiol group(s) essential for enzyme activity. Incubation of intact lymphocytes or lymphoblastoid cells with 2- or 6-mercaptopurine resulted in a decrease in Fru-2,6-P2 content and lactate release. A decrease in Fru-2,6-P2 content but no change in lactate release was observed in HeLa cells and fibroblasts treated with 6-mercaptopurine but not with 2-mercaptopurine. Treatment of HeLa cells with 6-mercaptopurine resulted in a decreased PFK-2 activity which could be restored by treatment of the cell extract with dithiothreitol. In isolated rat hepatocytes and perfused rat hearts mercaptopurines had little or no effect on the Fru-2,6-P2 content and lactate release. These results suggest that the effect of 6-mercaptopurine of arresting growth in lymphoid cells might involve the inhibition of glycolysis in addition to the known inhibition of de novo purine nucleotide synthesis.
6-磷酸果糖-2-激酶（PFK-2）可催化果糖2,6-二磷酸（Fru-2,6-P2）的合成，该酶的活性在体外受到巯基嘌呤的抑制。在大鼠肝脏和牛心脏的纯化酶中，以及在大鼠淋巴细胞和肝癌细胞、鸡胚成纤维细胞、人宫颈癌细胞（HeLa）和淋巴母细胞样细胞的提取物中均观察到了抑制作用。0.1 - 0.2 mM的巯基嘌呤可产生半数最大效应，最大抑制率在50%至90%之间，具体取决于酶制剂。这种抑制是由于Vmax降低，而ATP的Km值不变。用巯基还原剂处理该酶可解除抑制，这表明抑制作用涉及巯基嘌呤与酶活性所必需的巯基之间形成混合二硫键。用2-巯基嘌呤或6-巯基嘌呤孵育完整的淋巴细胞或淋巴母细胞样细胞，会导致Fru-2,6-P2含量和乳酸释放减少。在用6-巯基嘌呤而非2-巯基嘌呤处理的HeLa细胞和成纤维细胞中，观察到Fru-2,6-P2含量减少，但乳酸释放没有变化。用6-巯基嘌呤处理HeLa细胞会导致PFK-2活性降低，用二硫苏糖醇处理细胞提取物可恢复该活性。在分离的大鼠肝细胞和灌注的大鼠心脏中，巯基嘌呤对Fru-2,6-P2含量和乳酸释放几乎没有影响。这些结果表明，6-巯基嘌呤对淋巴细胞生长的抑制作用，除了已知的对嘌呤核苷酸从头合成的抑制外，可能还涉及对糖酵解的抑制。
