Platelet-activating factor modulates a secreted phosphatase activity of the trypanosomatid parasite Herpetomonas muscarum muscarum

In the present work we characterized the secreted phosphatase activity of t he trypanosomatid parasite Herpetomonas muscarum muscarum. This housefly pa rasite hydrolyzed p-nitrophenylphosphate at a rate of 10.26 nmol Pi/mg prot ein/min. Classical inhibitors of acid phosphatases, such as sodium orthovan adate (NaVO3), sodium fluoride (NaF), and ammonium molybdate promoted a dec rease in this phosphatase activity. When the parasites were assayed in the presence of sodium tartrate, an inhibitor of Leishmania spp-secreted acid p hosphatases, this activity was drastically diminished. Cytochemical analysi s showed the localization of this enzyme on the external surface and in the flagellar pocket of these parasites. Sodium tartrate inhibited this reacti on, confirming the biochemical data. Platelet-activating factor (PAF) inhib ited the phosphatase activity determined in the supernatant of living H. m. muscarum.