The effect of buthionine sulfoximine on the growth ofLeishmania donovaniin culture

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Abstract
Changes in composition of the principal low molecular mass thiols of Leishmania donovani were monitored during the transformation of promastigotes, first to stationary phase metacyclic forms and then to amastigotes. No consistent variation in the thiol composition of the parasite which could account for the known increase in resistance of metacyclic and amastigote lifecycle forms to oxidant stress could be established. Amastigotes cultivated at 37°C also produced ovothiol A, as judged by incorporation of radiolabel from [3-methyl]methionine and [14C]histidine, and the incorporation of radiolabel from [35S]cysteine into ovothiol A represented about 10–15% of the total label recovered in ovothiol A, glutathione and trypanothione. Amastigotes were less susceptible than promastigotes to the effects of the redox cyclers paraquat and menadione and grew in culture in the presence of up to 20 mM buthionine sulfoximine, which completely blocked the synthesis of glutathione and its spermidine conjugates. Glutathione and trypanothione biosynthesis is, therefore, not necessary for the replication of L. donovani amastigotes in culture. Inhibition of the formation of glutathione and trypanothione did not result in an upregulation of ovothiol A production.
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