Thymidine kinase and uridine-cytidine kinase from Entamoeba histolytica: cloning, characterization, and search for specific inhibitors.
Entamoeba histolytica is an intestinal parasite and the causative agent of amoebiasis, which is a significant source of morbidity and mortality in developing countries. Although anti-amoebic drugs such as metronidazole, emetine, chloroquine and nitazoxanide are generally effective, there is always potential for development of drug resistance. In order to find novel targets to control E. histolytica proliferation we cloned, expressed and purified thymidine kinase (Eh-TK) and uridine-cytidine kinase (Eh-UCK) from E. histolytica. Eh-TK phosphorylates thymidine with a Km of 0.27 microm, whereas Eh-UCK phosphorylates uridine and cytidine with Km of 0.74 and 0.22 mM, respectively. For both enzymes, ATP acts as specific phosphate donor. In order to find alternative treatments of E. histolytica infection we tested numerous nucleoside analogues and related compounds as inhibitors and/or substrates of Eh-TK and Eh-UCK, and active compounds against E. histolytica in cell culture. Our results indicate that inhibitors or alternative substrates of the enzymes, although partially reducing protozoan proliferation, are reversible and not likely to become drugs against E. histolytica infections.
Istituto di Genetica Molecolare, CNR, Pavia, Italy.
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A
Lossani
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Torti
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S
Gatti
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Bruno
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Maserati
G E
GE
Wright
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F
Focher
D000595:Amino Acid Sequence; D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D049109:Cell Proliferation; D003001:Cloning, Molecular; D004748:Entamoeba histolytica / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014541:Uridine Kinase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D000981:Antiprotozoal Agents; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D013937:Thymidine Kinase; D014541:Uridine Kinase