Dzik J M, Zieliński Z, Cieśla J, Bretner M, Kulikowski T, Shugar D, Bertino J R, Rode W
Nencki Institute of Experimental Biology, Academy of Sciences, Warszawa, Poland.
Biochem Biophys Res Commun. 1993 Sep 30;195(3):1301-8. doi: 10.1006/bbrc.1993.2185.
To determine how 5-fluoro-dUMP modifications may affect its specificity, 2-thio-5-fluoro-dUMP and 4-thio-5-fluoro-dUMP were compared as inhibitors of thymidylate synthases isolated from parental and FdUrd-resistant mouse leukemia L1210 cells, human and rat colon adenocarcinomas, regenerating rat liver and the tapeworm, Hymenolepis diminuta, differing in sensitivity to time- and N5,10-methylenetetrahydrofolate-dependent inactivation by 5-fluoro-dUMP (Ki values ranging from 10(-9) to 10(-7) M). Inactivation by 2-thio-5-fluoro-dUMP, relative to 5-fluoro-dUMP, was 5-20-fold weaker, with specificity for inactivation of different thymidylate synthases paralleling that of 5-fluoro-dUMP. By contrast, 4-thio-5-fluoro-dUMP showed very different specificity, being as potent an inactivator for some enzymes as 5-fluoro-dUMP, but 45-85-fold weaker for others. The results suggest that an interplay between substituents at C(4) and C(5) of the pyrimidine ring may affect the specificity of thymidylate synthase inactivation.
为了确定5-氟-dUMP修饰如何影响其特异性，将2-硫代-5-氟-dUMP和4-硫代-5-氟-dUMP作为从亲本和耐FdUrd的小鼠白血病L1210细胞、人及大鼠结肠腺癌、再生大鼠肝脏和绦虫微小膜壳绦虫中分离的胸苷酸合酶抑制剂进行比较，这些来源的胸苷酸合酶对5-氟-dUMP的时间依赖性和N5,10-亚甲基四氢叶酸依赖性失活的敏感性不同（Ki值范围为10(-9)至10(-7)M）。相对于5-氟-dUMP，2-硫代-5-氟-dUMP的失活作用弱5至20倍，其对不同胸苷酸合酶失活的特异性与5-氟-dUMP相似。相比之下，4-硫代-5-氟-dUMP表现出非常不同的特异性，对某些酶而言，它作为失活剂的效力与5-氟-dUMP相当，但对其他酶则弱45至85倍。结果表明，嘧啶环C(4)和C(5)位取代基之间的相互作用可能会影响胸苷酸合酶失活的特异性。
