Extracellular dephosphorylation in the parasite, Leishmania major.

Leishmania major promastigotes were analyzed for the presence of protein phosphatase activity in intact cells and membrane-enriched fractions. Parasite phosphoproteins, phosphorylated in live cells with [gamma-32P]adenosine 5'-triphosphate (ATP) and an endogenous leishmanial ectokinase, were dephosphorylated by endogenous protein phosphatase-like activity in intact cells and a membrane-rich fractions. An alkaline phosphatase-like activity was also identified using the artificial substrate, p-nitrophenyl phosphate (pNPP). This activity was localized on the extracellular membrane of intact parasites, as well as in the particulate fraction of lysed cells. The phosphatase activity measure using pNPP had inhibition properties and a pH profile between protein phosphatase and general alkaline phosphatases. This study supports the observation that there is extracellular protein phosphorylation/dephosphorylation in L. major which may play a significant role in host cell-parasite recognition and infection.