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 µM) but also deoxycytidine (Km 0.88 µM) and deoxyuridine (Km 0.14 µM). 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. vaginaliscultured cells and T. vaginalis growth (IC50 7.5 and 24 µM respectively; minimal lethal dose 100 µM). 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.
Trichomonas vaginalis thymidine kinase: purification, characterization and search for inhibitors
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Silvia STROSSELLI, Silvio SPADARI, Richard T. WALKER, Ivan BASNAK, Federico FOCHER; Trichomonas vaginalis thymidine kinase: purification, characterization and search for inhibitors. Biochem J 15 August 1998; 334 (1): 15–22. doi: https://doi.org/10.1042/bj3340015
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