title: Entamoeba histolytica: an ecto-phosphatase activity regulated by oxidation-reduction reactions.
abstract: In this work, an ecto-phosphatase activity of Entamoeba histolytica was characterized using intact cells. This activity presented the following biochemical characteristics: (i) it hydrolyzes p-NPP with V(max) of 8.00+/-0.22 nmol p-NP x h(-1) x 10(-5) cells and K(m) of 2.68+/-0.25 mM; (ii) it is inhibited by acid phosphatase inhibitors, such as sodium molybdate (K(i)=1.70+/-0.24 microM) and sodium fluoride (K(i)=0.25+/-0.02 mM); (iii) it also showed high sensitivity to phosphotyrosine phosphatase inhibitors, such as sodium orthovanadate (K(i)=1.07+/-0.14 microM), bpV-PHEN (K(i)=0.38+/-0.02 microM) and mpV-PIC (K(i)=0.39+/-0.04 microM). Zn(2+), an oxidizing agent, decreased the enzymatic activity in 50%. DTT and GSH, two reducing agents, enhanced the activity twofold. The non-invasive E. histolytica and free-living E. moshkovskii were less efficient in hydrolyzing p-NPP than the pathogenic E. histolytica suggesting that this enzyme could represent a virulence marker for this cell.
authors.affiliation: Instituto de Bioquímica Médica, UFRJ, Rio de Janeiro, RJ, Brazil.
authors.forename: Ana Acacia
authors.initials: AA
authors.lastname: de Sá Pinheiro
authors.forename: Juliana Natal
authors.initials: JN
authors.lastname: Amazonas
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Souza Barros
authors.forename: Lúcia Feitosa
authors.initials: LF
authors.lastname: De Menezes
authors.forename: Evander J O
authors.initials: EJ
authors.lastname: Batista
authors.forename: Edward Felix
authors.initials: EF
authors.lastname: Silva
authors.forename: Wanderley
authors.initials: W
authors.lastname: De Souza
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Meyer-Fernandes
mesh_terms: D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D003545:Cysteine / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004748:Entamoeba histolytica / Q000201:enzymology* / Q000472:pathogenicity; D005978:Glutathione / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008982:Molybdenum / Q000494:pharmacology; D009596:Nitrophenols / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010084:Oxidation-Reduction; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D014774:Virulence; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D002712:Chlorides; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D017967:Zinc Compounds; C008644:nitrophenylphosphate; D006639:Histidine; D008982:Molybdenum; C016837:zinc chloride; D012969:Sodium Fluoride; C024687:sodium molybdate(VI); D010744:Phosphoric Monoester Hydrolases; D005978:Glutathione; D003545:Cysteine; D004229:Dithiothreitol