A novel Sucrose/H+ Symport System and an Intracellular Sucrase in Leishmania Donovani.

Singh, Arpita and Mandal, Debjani (2011) A novel Sucrose/H+ Symport System and an Intracellular Sucrase in Leishmania Donovani. International Journal for Parasitology, 41 (8). pp. 817-826.


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    The flagellated form of pathogenic parasitic protozoa Leishmania, resides in the alimentary tract of its sandfly vector, where sucrose serves as a major nutrient source. In this study we report the presence of a sucrose transport system in Leishmania donovani promastigotes. The kinetics of sucrose uptake in promastigotes are biphasic in nature with both high affinity Km (Km of �75 lM) and low affinity Km (Km � 1.38 mM) components. By contrast the virulent amastigotes take up sucrose via a low affinity process with a Km of 2.5 mM. The transport of sucrose into promastigotes leads to rapid intracellular acidification, as indicated by changes in the fluorescence of the pH indicator 20,70-bis-(2-carboxyethyl)-5-(6) Carboxyfluorescein (BCECF). In experiments with right side-out plasma membrane vesicles derived from L. donovani promastigotes, an artificial pH gradient was able to drive the active accumulation of sucrose. These data are consistent with the operation of a H+-sucrose symporter. The symporter was shown to be independent of Na+ and to be insensitive to cytochalasin B, to the flavonoid phloretin and to the Na+/K+ ATPase inhibitor ouabain. However, the protonophore carbonylcyanide P- (trifluromethoxy) phenylhydrazone (FCCP) and a number of thiol reagents caused significant inhibition of sucrose uptake. Evidence was also obtained for the presence of a stable intracellular pool of the sucrose splitting enzyme, sucrase, in promastigote stage parasites. The results are consistent with the hypothesis that L. donovani promastigotes take up sucrose via a novel H+–sucrose symport system and that, on entering the cell, the sucrose is hydrolysed to its component monosaccharides by an intracellular sucrase, thereby providing an energy source for the parasites

    Item Type: Article
    URI: http://www.eprints.iicb.res.in/id/eprint/1274
    Subjects: Infectious Diseases and Immunology
    Divisions: Indian Institute of Chemical Biology
    Depositing User: Ms Sutapa Ganguly
    Date Deposited: 19 Jan 2012 15:42
    Last Modified: 19 Jan 2012 15:42
    Official URL: http://dx.doi.org/10.1016/j.ijpara.2011.03.004

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