Ecto-phosphatase activity on the cell surface of Crithidia deanei.
In the present work we have partially characterized an ecto-phosphatase activity in Crithidia deanei, using viable parasites. This enzyme hydrolyzed p-nitrophenylphosphate at a rate of 3.55 +/- 0.47 nmol Pi/h x 10(8) cells. The dependence on p-NPP concentration shows a normal Michaelis-Menten kinetics for this phosphatase activity and the value of the apparent Km for p-NPP was 5.35 +/- 0.89 mM. This phosphatase activity was inhibited by the product of the reaction, the inorganic phosphate. Experiments using classical inhibitors of acid phosphatases, such as ZnCl2 and sodium fluoride, as well as inhibitors of phosphotyrosine phosphatase, such as sodium orthovanadate and ammonium molybdate, showed a decrease in this phosphatase activity, with different patterns of inhibition.
dos Passos Lemos
Adriana
A
Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil.
Fonseca de Souza
André Luís
AL
de Sá Pinheiro
Ana Acacia
AA
de Berrêdo-Pinho
Márcia
M
Meyer-Fernandes
José Roberto
JR
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D003421:Crithidia / Q000201:enzymology*; D007700:Kinetics; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity
D010744:Phosphoric Monoester Hydrolases