A novel ecto-phosphatase activity of Herpetomonas muscarum muscarum inhibited by platelet-activating factor

In the present work ecto-phosphatase activity in Herpetomonas muscarum musc arum has been characterized using live parasites. This enzyme hydrolyzed p- nitrophenylphosphate at a rate of 4.27 nmol P-i/mg of protein min. A pH cur ve was generated, in which these intact flagellates showed the highest phos phatase activity at pH 6.5. Classical inhibitors for acid phosphatase, such as sodium orthovanadate, sodium tartrate, and ammonium molybdate, were use d in the experiments and showed different patterns of inhibition. Lithium f luoride, aluminum chloride, and fluoroaluminate complexes were also tested. Although lithium fluoride and fluoroaluminate complexes were capable of in hibiting the phosphatase activity, aluminum chloride stimulated this enzyme . Cytochemical analysis showed the localization of this enzyme on the paras ite surface. This ecto-phosphatase activity was also significantly diminish ed when the parasites were treated with 10(-6) M platelet-activating factor (PAF), a potent phospholipid mediator that promoted cellular differentiati on in this parasite. (C) 1998 Academic Press.