title: Entamoeba histolytica: ouabain-insensitive Na(+)-ATPase activity.
abstract: Our aim was to determine the presence of sodium pumps in Entamoeba histolytica. It is shown through the measurement of ouabain-sensitive ATPase activity and immunoblotting that E. histolytica does not express (Na(+)+K(+))ATPase. On the other hand, we observed a Na(+)-ATPase with the following characteristics: (1) stimulated by Na(+) or K(+), but these effects are not addictive; (2) the apparent affinity is similar for Na(+) and K(+) (K(0.5) = 13.3 +/- 3.7 and 15.4 +/- 3.1mM, respectively), as well as the V(max) (24.9 +/- 1.5 or 27.5 +/- 1.6 nmol Pi mg(-1)min(-1), respectively); (3) insensitive up to 2mM ouabain; and (4) inhibited by furosemide with an IC(50) of 0.12 +/- 0.004 mM. Furthermore, this enzyme forms a Na(+)- or K(+)-stimulated, furosemide- and hydroxylamine-sensitive ATP-driven acylphosphate phosphorylated intermediate.
authors.affiliation: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, RJ, Brazil.
authors.forename: Aloa M
authors.initials: AM
authors.lastname: De Souza
authors.forename: Evander J O
authors.initials: EJ
authors.lastname: Batista
authors.forename: Ana Acácia de S
authors.initials: AA
authors.lastname: Pinheiro
authors.forename: Mariana
authors.initials: M
authors.lastname: Carvalhaes
authors.forename: Aníbal G
authors.initials: AG
authors.lastname: Lopes
authors.forename: Wanderley
authors.initials: W
authors.lastname: De Souza
authors.forename: Celso
authors.initials: C
authors.lastname: Caruso-Neves
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004748:Entamoeba histolytica / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005665:Furosemide / Q000494:pharmacology; D015151:Immunoblotting; D007672:Kidney Cortex / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology*; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013552:Swine
chemical_list: D027682:Cation Transport Proteins; D004791:Enzyme Inhibitors; D049994:Sodium Potassium Chloride Symporter Inhibitors; D010042:Ouabain; D005665:Furosemide; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D000254:Sodium-Potassium-Exchanging ATPase