Secreted phosphatase activities in trypanosomatid parasites of plants modulated by platelet-activating factor.

The secreted phosphatase activities of two trypanosomatid parasites were ch aracterized and compared with supernatants of living cells. The plant paras ite Phytomonas francai and the phytophagous hemipteran parasite Herpetomona s sp. hydrolyzed p-nitrophenylphosphate at a rate of 15.54 and 6.51 nmol Pi /mg of protein per min, respectively. Sodium orthovanadate (NaVO3) and sodi um fluoride (NaF) decreased the phosphatase activities. The phosphatase act ivity of P. francai was drastically diminished (73% inhibition) in the pres ence of sodium tartrate, whereas the phosphatase activity of Herpetomonas s p, was inhibited by 23%. Cytochemical analysis showed the localization of t hese enzymes on the external surface and in the flagellar pocket of the two trypanosomatids. Sodium tartrate inhibited this reaction, confirming the b iochemical data. Platelet-activating factor modulated the phosphatase activ ities, inhibiting P. francai activity and stimulating Herpetomonas sp. phos phatase activity.