Carlos Eduardo Peres-Sampaio

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The plasma membrane of cells contains enzymes whose active sites face the external medium rather than the cytoplasm. The activities of these enzymes, referred to as ectoenzymes, can be measured using living cells. In this work we describe the ability of living promastigotes of Leishmania amazonensis to hydrolyze extracellular ATP. In these intact parasites(More)
In this study we report the effects of sulfated polysaccharides on the ecto-ATPase activity of intact cells of Leishmania tropica. Increasing concentrations of dextran sulfate stimulated progressively the ecto-ATPase activity, but did not modify other ecto-enzymes present on the surface of this parasite, such as 5'nucleotidase, 3'nucleotidase and a(More)
This study describes the possible role of Mg2+-dependent ecto-ATPase activity on the Trypanosoma cruzi–host cell interaction. Mg2+-dependent ecto-ATPase activity is observed on the cell body and flagellar membranes of the parasite and is about 20 times greater in trypomastigotes, as compared with epimastigotes. Suramin (a competitive antagonist of P2(More)
Cell viability requires the perfect functioning of the processes controlling ATP and Ca(2+) homeostasis. It is known that cell death caused by a variety of toxins or pathological conditions is associated with a disruption of ATP and Ca(2+) homeostasis. This study shows that 4,4'-diisothyocyanatostilbene-2,2'-disulfonic acid (DIDS) inhibits Trypanosoma cruzi(More)
We show that urea inhibits the ATPase activity of MgATP submitochondrial particles (MgATP-SMP) with Ki = 0.7 M, probably as a result of direct interaction with the structure of F0F1-ATPase. Counteracting compounds (sorbitol, mannitol or inositol), despite slightly (10-20%) inhibiting the ATPase activity, also protect the F0F1-ATPase against denaturation by(More)
In this work, we describe the ability of living epimastigotes of Trypanosoma cruzi to hydrolyze extracellular ATP. In these intact parasites, there was a low level of ATP hydrolysis in the absence of any divalent metal (2.42±0.31 nmol Pi/h×108 cells). ATP hydrolysis was stimulated by MgCl2, and the Mg-dependent ecto-ATPase activity was 27.15±2.91 nmol(More)
The plasma membrane (Ca(2+) + Mg(2+))ATPase hydrolyzes pseudo-substrates such as p-nitrophenylphosphate. Except when calmodulin is present, Ca(2+) ions inhibit the p-nitrophenylphosphatase activity. In this report it is shown that, in the presence of glycerol, Ca(2+) strongly stimulates phosphatase activity in a dose-dependent manner. The glycerol- and(More)
In this work we demonstrated that promastigotes of Leishmania amazonensis exhibit an Mg-dependent ecto-ATPase activity, which is stimulated by heat shock. The Mg-dependent ATPase activity of cells grown at 22 and 28 degrees C was 41.0+/-5.2 nmol Pi/h x 10(7)cells and 184.2+/-21.0 nmol Pi/h x 10(7)cells, respectively. When both promastigotes were(More)
Adriana dos Passos Lemos, Carlos E. Peres-Sampaio, Horácio Guimarães-Motta, Jerson L. Silva and José R. Meyer-Fernandes* Departamento de Bioqmmica Medica, Instituto de Ciencias Biomedicas, Universidade Federal do Rio de Janeiro (UFRJ), Ilha do Fundäo, 21941-590. Rio de Janeiro, RJ. Brazil. Fax: (+55) (+21) 270-8647. E-mail: * Author(More)
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