Trichomonas vaginalis thymidine kinase: purification, characterization and search for inhibitors.
We report that a thymidine kinase (TK) activity is present in Trichomonas vaginalis and can be separated from the deoxyribonucleoside phosphotransferase. T. vaginalis TK, purified 11200-fold to apparent homogeneity, has a molecular mass of 31500 Da. It phosphorylates not only thymidine (Km 0.18 microM) but also deoxycytidine (Km 0.88 microM) and deoxyuridine (Km 0.14 microM). In contrast with T. vaginalis deoxyribonucleoside phosphotransferase, the TK activity is strongly inhibited by novel deoxyuridine analogues such as 5-methyl-4'-thio-2'-deoxyuridine (MTdU) (Ki 20 nM) and 5-iodo-4'-thio-2'-deoxyuridine (ITdU) (Ki 24 nM). MTdU and ITdU are phosphorylated by T. vaginalis TK in vitro. In vivo they inhibit [3H]thymidine incorporation in T. vaginalis cultured cells and T. vaginalis growth (IC50 7.5 and 24 microM respectively; minimal lethal dose 100 microM). Thus the TK inhibitors described here demonstrate the key role of T. vaginalis TK for protozoal growth and viability and indicate TK as a new target for the design of antitrichomonal drugs.
Istituto di Genetica Biochimica ed Evoluzionistica, CNR, via Abbiategrasso 207, 27100 Pavia, Italy.
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Strosselli
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Spadari
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Walker
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Basnak
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Focher
D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014246:Trichomonas vaginalis / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development
D000981:Antiprotozoal Agents; D004791:Enzyme Inhibitors; D013937:Thymidine Kinase; D003857:Deoxyuridine