Giardia lamblia: Characterization of ecto-phosphatase activities.
Ecto-phosphatase activities of Giardia lamblia were characterized in intact cells, which are able to hydrolyze the artificial substrate p-nitrophenylphosphate (p-NPP) to p-nitrophenol (p-NP) at a rate of 8.4+/-0.8 nmol p-NP/h/10(7) cells. The ecto-phosphatase activities were inhibited at high pH as well as by classical inhibitors of acid phosphatases, such as sodium fluoride and sodium molybdate and by inorganic phosphate, the final product of the reaction. Experiments using a classical inhibitor of phosphotyrosine phosphatase, sodium orthovanadate, also showed that the ecto-phosphatase activity was inhibited in a dose-dependent manner. Different phosphorylated amino acids were used as substrates for the G. lamblia ecto-phosphatase activities the highest rate of phosphate release was achieved using phosphotyrosine. Not only p-NPP hydrolysis but also phosphotyrosine hydrolysis was inhibited by sodium orthovanadate. Phosphotyrosine but not phospho-serine or phospho-threonine inhibited the p-nitrophenylphosphatase activity. We also observed a positive correlation between the ecto-phosphatase activity and the capacity to encystation of G. lamblia trophozoites.
Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, CCS, Bloco H, sala H2-013, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil.
Juliana Natal
JN
Amazonas
Daniela
D
Cosentino-Gomes
Aline
A
Werneck-Lacerda
Ana Acácia de Sá
AA
Pinheiro
Adriana
A
Lanfredi-Rangel
Wanderley
W
De Souza
José R
JR
Meyer-Fernandes
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016829:Giardia lamblia / Q000201:enzymology* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008982:Molybdenum / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D013379:Substrate Specificity; D014638:Vanadates / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014638:Vanadates; D008982:Molybdenum; D012969:Sodium Fluoride; C024687:sodium molybdate(VI); D010744:Phosphoric Monoester Hydrolases