EXTRACELLULAR RELEASE BY TRICHOMONAS-VAGINALIS OF A NADP(+) DEPENDENTMALIC ENZYME INVOLVED IN PATHOGENICITY

This This report presents evidence showing that Trichomonas vaginalis releases in the extracellular environment a functional form of NADP(+) -dependent malic enzyme. The protein which is likely responsible for t he oxidative decarboxilase activity had already been identified in pre vious studies as P65, one of the five adhesive proteins of the protozo an. The same protein had also been described as AP65 by other authors, which identified it as one of the four surface proteins specifically responsible for binding of the parasite to the target cell in a ligand -receptor fashion. Gene characterization studies performed on P65 by d ifferent authors revealed that the nucleotide sequences of the genes c oding for P65 display a striking homology with the ones coding for the trichomonad malic enzyme. The experiments performed in this work demo nstrate that P65 is secreted and retains its adhesive properties in th e extracellular environment, being able to bind both erythrocytes and HeLa cells. Therefore, an oxidative decarboxylase activity assay was p erformed on T. vaginalis cell-free filtrates, in order to assess if th e released P65 displays cathalitic properties. The assay revealed that parasite-free supernatants exhibit an oxidative decarboxylase activit y which is NADP(+)-dependent. On the basis of the most recent findings on T. vaginalis pathogenetic mechanism, which involves pH-dependent p erforins, a role for the secreted enzymes part of the system is propos ed. (C) 1997 Academic Press Limited.