Ahmed N, Weidemann M J
Division of Biochemistry and Molecular Biology, School of Life Sciences, Australian National University, Canberra.
Leuk Res. 1994 Jun;18(6):441-51. doi: 10.1016/0145-2126(94)90080-9.
Purine metabolism was studied in the human promyelocytic leukaemic cell line HL60 both before and after differentiation by dimethylsulphoxide (DMSO) treatment in vitro. DMSO-induced differentiation had no effect on the steady-state concentration of 5-phosphoribosylpyrophosphate (PRPP), even though the activity of the oxidative segment of the pentose phosphate pathway (OPP) increased two-fold and the activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were enhanced 3-6 times. [14C]-formate incorporation, on the other hand, showed that undifferentiated HL60 cells produced purines by the de novo pathway at six-fold the rate of the differentiated cells and at three times the rate measured in polymorphonuclear leukocytes (PMNs) separated from human blood. This is consistent with significantly higher activities (two to five-fold) of the key regulatory enzymes of the de novo purine synthesis pathway (PRPP synthetase, amido-phosphoribosyl transferase and adenylosuccinate synthase) in the undifferentiated cells. Labelling the cells with [14C]-hypoxanthine showed that there was an active salvage pathway in the HL60 cells which remained unaltered by differentiation. The activities of the salvage enzymes were also the same, although hypoxanthine was taken up at twice the rate by the undifferentiated cells. Human PMNs had an active salvage pathway, but their rate was five times lower than that of the HL60 cells, consistent with much lower activities (three to eight-fold) of the salvage pathway enzymes. These observations suggest that regulation of the synthesis and activities of the purine nucleotide synthesis enzymes may play an important role in the regulation of differentiation of myeloid cells.
在体外通过二甲基亚砜（DMSO）处理使人类早幼粒细胞白血病细胞系HL60分化前后，对其嘌呤代谢进行了研究。DMSO诱导的分化对5-磷酸核糖焦磷酸（PRPP）的稳态浓度没有影响，尽管磷酸戊糖途径（OPP）氧化段的活性增加了两倍，葡萄糖-6-磷酸脱氢酶和6-磷酸葡萄糖酸脱氢酶的活性增强了3至6倍。另一方面，[14C]-甲酸掺入显示，未分化的HL60细胞通过从头合成途径产生嘌呤的速率是分化细胞的6倍，是从人血中分离出的多形核白细胞（PMN）中测得速率的3倍。这与未分化细胞中从头嘌呤合成途径的关键调节酶（PRPP合成酶、酰胺磷酸核糖转移酶和腺苷酸琥珀酸合成酶）的活性显著更高（2至5倍）是一致的。用[14C]-次黄嘌呤标记细胞表明，HL60细胞中有一条活跃的补救途径，该途径不会因分化而改变。补救酶的活性也相同，尽管未分化细胞摄取次黄嘌呤的速率是其两倍。人类PMN有一条活跃的补救途径，但其速率比HL60细胞低5倍，这与补救途径酶的活性低得多（3至8倍）是一致的。这些观察结果表明，嘌呤核苷酸合成酶的合成和活性调节可能在髓系细胞分化调节中起重要作用。
