Trypanosoma rangeli: an alkaline ecto-phosphatase activity is involved with survival and growth of the parasite.

André L A Dos-Santos, Claudia F Dick, Thaís S Silveira, André L Fonseca-de-Souza, José R Meyer-Fernandes

Index: Exp. Parasitol. 135(2) , 459-65, (2013)

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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. Copyright © 2013 Elsevier Inc. All rights reserved.