Ecto-ATPases in protozoa parasites: looking for a function.
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 ecto-enzymes, can be measured using living cells. Cell membrane ecto-ATPases are integral membrane glycoproteins that are millimolar divalent cation-dependent, low specificity enzymes that hydrolyze all nucleoside triphosphates. Their physiological role is still unknown. However, several hypotheses have been suggested such as; (i). protection from cytolytic effects of extracellular ATP, (ii). regulation of ectokinase substrate concentration, (iii). termination of purinergic signaling, (iv). involvement in signal transduction, and (v). involvement in cellular adhesion. In this review, the biochemical properties and possible functions of the ecto-ATPases of different protozoa are summarized.
Roberto Meyer-Fernandes
José
J
Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, CCS, Bloco H-20 andar-sala 13, Cidade Universitária, Ilha do Fundão, 21541-590, RJ, Rio de Janeiro, Brazil. meyer@bioqmed.ufrj.br
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion; D056890:Eukaryota / Q000201:enzymology* / Q000472:pathogenicity; D006801:Humans; D011528:Protozoan Infections / Q000469:parasitology
D000251:Adenosine Triphosphatases; C027201:ectoATPase