Slingerland R J, Van Gennip A H, Bodlaender J M, Voûte P A, Van Kuilenburg A B
Academic Medical Center, University of Amsterdam, The Netherlands.
Eur J Biochem. 1995 Oct 15;233(2):538-43. doi: 10.1111/j.1432-1033.1995.538_2.x.
A detailed quantitative study of pyrimidine metabolism in exponentially growing rat pheochromocytoma PC-12 cells has been performed. The sizes of ribonucleotide pools have been analysed and the pathways and the rates of metabolism of uridine, cytidine and aspartic acid have been determined, based on the incorporation of radioactive label. The fluxes of radioactive label through uridine-cytidine kinase, cytidine deaminase. CTP synthetase, nucleoside monophosphate kinase and nucleoside diphosphate kinase were obtained, as well as the flux through the pyrimidine de novo pathway. Also, the fluxes of radioactive label towards UDP-sugars, CDP-compounds, DNA and RNA were quantified in situ under steady-state conditions in intact PC-12 cells. From these fluxes of radioactivity, distribution ratios at the branch points of the metabolism were obtained. The pyrimidines synthesised via the de novo pathway were preferentially used for the synthesis of UDP-N-acetylhexosamines and UDP-hexoses, whereas the salvage of precursors from the medium contributed, to a large extent, to the synthesis of RNA. Therefore, we postulate that at least two different UTP pools exist in these cancer cells derived from the neural crest. Furthermore, after metabolism of radiolabeled cytidine and uridine into UTP, radiolabel was distributed in a similar manner from UTP towards UDP-N-acetylhexosamines, UDP-hexoses and RNA-UMP. Uridine, as well as cytidine, was channelled towards nucleic acids via small compartmented ribonucleotide pools.
已对指数生长的大鼠嗜铬细胞瘤PC-12细胞中的嘧啶代谢进行了详细的定量研究。分析了核糖核苷酸池的大小，并基于放射性标记的掺入确定了尿苷、胞苷和天冬氨酸的代谢途径及代谢速率。获得了放射性标记通过尿苷-胞苷激酶、胞苷脱氨酶、CTP合成酶、核苷单磷酸激酶和核苷二磷酸激酶的通量，以及通过嘧啶从头合成途径的通量。此外，在完整的PC-12细胞的稳态条件下，原位定量了放射性标记向UDP-糖、CDP-化合物、DNA和RNA的通量。从这些放射性通量中，获得了代谢分支点处的分配比。通过从头合成途径合成的嘧啶优先用于UDP-N-乙酰己糖胺和UDP-己糖的合成，而从培养基中挽救前体在很大程度上有助于RNA的合成。因此，我们推测在这些源自神经嵴的癌细胞中至少存在两个不同的UTP池。此外，在将放射性标记的胞苷和尿苷代谢为UTP后，放射性标记从UTP向UDP-N-乙酰己糖胺、UDP-己糖和RNA-UMP的分布方式相似。尿苷以及胞苷通过小的分隔核糖核苷酸池被导向核酸。
