GOLGI ASSOCIATED PHOSPHOHYDROLASES IN TRYPANOSOMA BRUCEI

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Various parasitic protozoa of the family Trypanosomatidae have been shown to contain acid phosphatase activity. It had been shown by others Trypanosoma brucei contains tartrate-sensitive and tartrate-insensitive acid phosphatases which are equally distributed together between the flagella pocket and cell membrane (McLaughlin et al. Can J Biochem 54 365, l976; Schell et al. FEBS Letters 271 67, l990). We have shown, in T. brucei, that acid phosphatrase activity was highest in the Gogi membrane frations (Grab et al. J Cell Biol 105 737, l987). Although some of this enzyme activity may also be found on purified lysosomes and flagella pocket membranes, the levels in these compartments are considerably lower. Using the powerful technique of preparative free flow electrophoresis (FFE) we find that Golgi-associated tartrate sensitive acid phosphatase(s) is located in a trans-Golgi subcompartment. In addition to hydrolysis of classical acid phosphatase substrates, prelimenary data suggest that Golgi membranes may utilize myo-1 and myo-2-inositol phosphates, as well as myo-1,2-cyclic inositol phosphate. The data suggest that Golgi acid phosphatase may play an important role in parasite inositol metabolism. In addition, hydrolysis of cyclic inositol phosphate also suggest that the enzyme(s) could play a role in glycosylphophatidylinositol (GPI) anchor metabolism and possibly recycling of the major GPI-anchored variable surface glycoprotein (VSG) present on African trypansomes.