title: A Mg-dependent ecto-ATPase is increased in the infective stages of Trypanosoma cruzi.
abstract: 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 x 10(8) cells). ATP hydrolysis was stimulated by MgCl2, and the Mg-dependent ecto-ATPase activity was 27.15 +/- 2.91 nmol Pi/h x 10(8) cells. The addition of MgCl2 to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. This stimulatory activity was also observed when MgCl2 was replaced by MnCl2, but not by CaCl2 or SrCl2. The apparent Km for Mg-ATP2- was 0.61 mM, and free Mg2+ did not increase the ecto-ATPase activity. This ecto-ATPase activity was insensitive to the inhibitors of other ATPase and phosphatase activities. To confirm that this Mg-dependent ATPase was an ecto-ATPase, we used an impermeant inhibitor, DIDS (4, 4'.diisothiocyanostylbene 2'-2'-disulfonic acid) as well as suramin, an antagonist of P2 purinoreceptors and inhibitor of some ecto-ATPases. These two reagents inhibited the Mg2+-dependent ATPase activity in a dose-dependent manner. A comparison among the Mg2+-ecto-ATPase activities of the three forms of T. cruzi showed that the noninfective epimastigotes were less efficient at hydrolyzing ATP than the infective trypomastigote and amastigote stages.
authors.affiliation: Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, CCS, Bloco H, Cidade Universitária, Ilha do Fundão, 21541-590 Rio de Janeiro, RJ, Brazil. meyer@bioqmed.ufrj.br
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Meyer-Fernandes
authors.forename: Jorge
authors.initials: J
authors.lastname: Saad-Nehme
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Peres-Sampaio
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Belmont-Firpo
authors.forename: Danielle F R
authors.initials: DF
authors.lastname: Bisaggio
authors.forename: Luciana C
authors.initials: LC
authors.lastname: Do Couto
authors.forename: André Luíz
authors.initials: AL
authors.lastname: Fonseca De Souza
authors.forename: Angela H S C
authors.initials: AH
authors.lastname: Lopes
authors.forename: Thais
authors.initials: T
authors.lastname: Souto-Padrón
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D008274:Magnesium / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000201:enzymology / Q000254:growth & development / Q000472:pathogenicity*; D015854:Up-Regulation; D014774:Virulence
chemical_list: D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D008274:Magnesium