title: Trypanosoma rangeli: an alkaline ecto-phosphatase activity is involved with survival and growth of the parasite.
abstract: The aim of this work was to investigate whether an alkaline ecto-phosphatase activity is present in the surface of Trypanosoma rangeli. Intact short epimastigote forms were assayed for ecto-phosphatase activity to study kinetics and modulators using β-glycerophosphate (β-GP) and p-nitrophenyl phosphate (pNPP) as substrates. Its role in parasite development and differentiation was also studied. Competition assays using different proportions of β-GP and pNPP evidenced the existence of independent and non-interacting alkaline and acid phosphatases. Hydrolysis of β-GP increased progressively with pH, whereas the opposite was evident using pNPP. The alkaline enzyme was inhibited by levamisole in a non-competitive fashion. The Ca(2+) present in the reaction medium was enough for full activity. Pretreatment with PI-PLC decreased the alkaline but not the acid phosphatase evidence that the former is catalyzed by a GPI-anchored enzyme, with potential intracellular signaling ability. β-GP supported the growth and differentiation of T. rangeli to the same extent as high orthophosphate (Pi). Levamisole at the IC50 spared significantly parasite growth when β-GP was the sole source of Pi and stopped it in the absence of β-GP, indicating that the alkaline enzyme can utilize phosphate monoesters present in serum. These results demonstrate the existence of an alkaline ecto-phosphatase in T. rangeli with selective requirements and sensitivity to inhibitors that participates in key metabolic processes in the parasite life cycle.
authors.affiliation: Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, 21941-590 Rio de Janeiro, Brazil.
authors.forename: André L A
authors.initials: AL
authors.lastname: Dos-Santos
authors.forename: Claudia F
authors.initials: CF
authors.lastname: Dick
authors.forename: Thaís S
authors.initials: TS
authors.lastname: Silveira
authors.forename: André L
authors.initials: AL
authors.lastname: Fonseca-de-Souza
authors.forename: José R
authors.initials: JR
authors.lastname: Meyer-Fernandes
mesh_terms: D000135:Acid Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism*; D002384:Catalysis; D002413:Cations, Divalent / Q000494:pharmacology; D005994:Glycerophosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007978:Levamisole / Q000494:pharmacology; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D013379:Substrate Specificity; D057509:Trypanosoma rangeli / Q000201:enzymology* / Q000254:growth & development*
chemical_list: D002413:Cations, Divalent; D005994:Glycerophosphates; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D007978:Levamisole; C008644:nitrophenylphosphate; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; C031463:beta-glycerophosphoric acid
keywords: Alkaline ecto-phosphatase; FBS; GPI; Inorganic phosphate acquisition; LIT; PI-PLC; Parasite differentiation; Parasite proliferation; Trypanosoma rangeli; fetal bovine serum; glycosylphosphatidyl inositol; liver infusion tryptose medium; p-nitrophenyl phosphate; pNPP; phosphatidylinositol-phospholipase C; β-GP; β-glycerophosphate