Cappiello M, Mascia L, Scolozzi C, Giorgelli F, Ipata P L
Department of Physiology and Biochemistry, University of Pisa, Via S. Maria 55, 56126 Pisa, Italy.
Biochim Biophys Acta. 1998 Oct 23;1425(2):273-81. doi: 10.1016/s0304-4165(98)00071-3.
In this paper we extend our previous observation on the mobilization of the ribose moiety from guanosine to xanthine catalyzed by rat liver extracts (Giorgelli et al., Biochim. Biophys. Acta 1335 (1997) 16-22). The data show that in rat liver and brain extracts the activated ribose, stemming from inosine and guanosine phosphorolysis as ribose 1-phosphate, can be used to salvage uracil to uracil nucleotides. Uridine is an intermediate. The salvage process occurs even in the presence of excess inorganic phosphate suggesting that uridine phosphorylase may function in vivo as an anabolic enzyme. Ribose 5-phosphate cannot substitute for inosine, guanosine or ribose 1-phosphate as ribose donor. When inorganic phosphate was substituted with arsenate, hindering the formation of ribose 1-phosphate, no ribose transfer could be observed. A similar pathway occurs at the deoxy level. The deoxyribose moiety of deoxyinosine can be used to salvage thymine to thymine nucleotides, again in the presence of excess inorganic phosphate. Our results introduce a novel aspect of the salvage pathway, in which ribose 1-phosphate seems to play a pivotal role.
在本文中，我们扩展了之前关于大鼠肝脏提取物催化鸟苷核糖部分转移至黄嘌呤的观察结果（乔尔杰利等人，《生物化学与生物物理学报》1335 (1997) 16 - 22）。数据表明，在大鼠肝脏和脑提取物中，由肌苷和鸟苷磷酸解产生的作为1 - 磷酸核糖的活化核糖，可用于将尿嘧啶挽救为尿嘧啶核苷酸。尿苷是中间产物。即使在存在过量无机磷酸盐的情况下，挽救过程仍会发生，这表明尿苷磷酸化酶在体内可能作为一种合成代谢酶发挥作用。5 - 磷酸核糖不能替代肌苷、鸟苷或1 - 磷酸核糖作为核糖供体。当用砷酸盐替代无机磷酸盐，从而阻碍1 - 磷酸核糖的形成时，未观察到核糖转移。类似的途径也发生在脱氧水平。脱氧肌苷的脱氧核糖部分可用于将胸腺嘧啶挽救为胸腺嘧啶核苷酸，同样是在存在过量无机磷酸盐的情况下。我们的结果引入了挽救途径的一个新方面，其中1 - 磷酸核糖似乎起着关键作用。
