title: Trypanosoma brucei: ecto-phosphatase activity present on the surface of intact procyclic forms.
abstract: The results presented in this paper indicate that procyclic forms of Trypanosoma brucei possess a phosphatase activity detected in the external cell surface able to hydrolyze about 0.7 nmol.mg-1.min-1 p-nitrophenylphosphate. A faster rate of hydrolysis was observed when membrane-enriched fractions were used. This activity is weakly sensitive to 1 mM NaF, 10 mM tartrate and 10 mM levamizole but strongly inhibited by 0.1 mM vanadate. Inhibition by both NaF and vanadate have a competitive character. This phosphatase activity decreases by increasing the pH from 6.8 to 8.4, a pH range in which cell viability was maintained during at least 1 hour. In the membrane-enriched fractions this phosphatase activity showed to be an acid phosphatase. In addition, intact cells could catalyze the dephosphorylation of [32P]phosphocasein phosphorylated at serine and threonine residues.
authors.affiliation: Departamento de Bioquímica, Universidade Estadual de Campinas, SP, Brazil.
authors.forename: E C
authors.initials: EC
authors.lastname: Fernandes
authors.forename: J R
authors.initials: JR
authors.lastname: Meyer-Fernandes
authors.forename: M A
authors.initials: MA
authors.lastname: Silva-Neto
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002729:Chloromercuribenzoates / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007978:Levamisole / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D013644:Tartrates / Q000494:pharmacology; D013773:Tetramisole / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000502:physiology*; D014638:Vanadates / Q000494:pharmacology; D020245:p-Chloromercuribenzoic Acid
chemical_list: D002729:Chloromercuribenzoates; D004791:Enzyme Inhibitors; D013644:Tartrates; D007978:Levamisole; D014638:Vanadates; D020245:p-Chloromercuribenzoic Acid; D012969:Sodium Fluoride; D013773:Tetramisole; D010744:Phosphoric Monoester Hydrolases; D009597:4-Nitrophenylphosphatase