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.
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.
Dzik
J M
JM
Nencki Institute of Experimental Biology, Academy of Sciences, Warszawa, Poland.
Zieliński
Z
Z
Cieśla
J
J
Bretner
M
M
Kulikowski
T
T
Shugar
D
D
Bertino
J R
JR
Rode
W
W
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005468:Fluorodeoxyuridylate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D006926:Hymenolepis / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D051379:Mice; D051381:Rats; D013873:Thionucleotides / Q000494:pharmacology*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured
D013873:Thionucleotides; C054543:5-fluoro-4-thio-2'-deoxyuridylate; D005468:Fluorodeoxyuridylate; C083360:5-fluoro-2-thio-2'-deoxyuridylate; D013940:Thymidylate Synthase