Interaction of 2-thio-5-fluoro-dUMP and 4-thio-5-fluoro-dUMP with mammalian normal and tumour and helminthic thymidylate synthases: influence of C (4) -substituents on specificity for enzyme inactivation
Dzik, J.M.; Zieliński, Z.; Cieśla, J.; Bretner, M.; Kulikowski, T.; Shugar, D.; Bertino, J.R.; Rode, W.
Biochemical and Biophysical Research Communications 195(3): 1301-1308
1993
ISSN/ISBN: 0006-291X PMID: 8216262 Document Number: 408337
2-thio-fluoro-dUMP and 4-thio-5-fluoro-dUMP were compared as inhibitors of thymidylate synthases to determine how 5-fluoro-dUMP modifications may affect its specificity. The thymidylate synthases were isolated from parental and FdUrd-resistant mouse leukaemia L1210 cells, human and rat colon adenocarcinomas, regenerating rat liver and Hymenolepis diminuta, differing in sensitivity to time- and N5,10-methylenetetrahydrofolate-dependent inactivation by 5-fluoro-dUMP. Inactivation by 2-thio-5-fluoro-dUMP was between 5 and 20 times weaker than inactivation by 5-fluoro-dUMP, with specificity for inactivation of different thymidylate synthases paralleling that of 5-fluoro-dUMP. In contrast, 4-thio-5-fluoro-dUMP showed very different specificity, being as potent an inactivator for some enzymes as 5-fluoro-dUMP but between 45 and 85 times weaker for others. Results suggested that an interplay between substituents at C(4) and C(5) of the pyrimidine ring may affect the specificity of thymidylate synthase inactivation.