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Extracellular release by Trichomonas vaginalis of a NADP+ dependent malic enzyme involved in pathogenicity
M F Addis1, P Rappelli, P Cappuccinelli
1Institute of Microbiology and Virology, University of Sassari, Italy.
Abstract:
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 the oxidative decarboxilase activity had already been identified in previous studies as P65, one of the five adhesive proteins of the protozoan. 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 different authors revealed that the nucleotide sequences of the genes coding for P65 display a striking homology with the ones coding for the trichomonad malic enzyme. The experiments performed in this work demonstrate that P65 is secreted and retains its adhesive properties in the extracellular environment, being able to bind both erythrocytes and HeLa cells. Therefore, an oxidative decarboxylase activity assay was performed on T. vaginalis cell-free filtrates, in order to assess if the released P65 displays cathalitic properties. The assay revealed that parasite-free supernatants exhibit an oxidative decarboxylase activity which is NADP(+)-dependent. On the basis of the most recent findings on T. vaginalis pathogenetic mechanism, which involves pH-dependent perforins, a role for the secreted enzyme as part of the system is proposed.
Insights
Trichomonas vaginalis secretes a protein, P65, that functions as an NADP(+)-dependent malic enzyme. This secreted enzyme retains adhesive properties, suggesting a role in parasite-host cell interactions and pathogenesis.
Area of Science:
- Biochemistry
- Parasitology
- Molecular Biology
Background:
- Trichomonas vaginalis possesses adhesive proteins, including P65 (also known as AP65), crucial for host cell binding.
- Previous studies indicated homology between the P65 gene and malic enzyme genes.
Purpose of the Study:
- To investigate the extracellular functional form of NADP(+)-dependent malic enzyme in Trichomonas vaginalis.
- To determine if the secreted P65 protein exhibits catalytic activity and retains adhesive properties.
Main Methods:
- Analysis of T. vaginalis cell-free filtrates for enzymatic activity.
- Assays to test the binding capabilities of secreted P65 to erythrocytes and HeLa cells.
- Oxidative decarboxylase activity assays on parasite-free supernatants.
Main Results:
- Trichomonas vaginalis releases a functional NADP(+)-dependent malic enzyme into the extracellular environment.
- The secreted P65 protein retains its adhesive properties, binding to both erythrocytes and HeLa cells.
- Parasite-free supernatants demonstrated NADP(+)-dependent oxidative decarboxylase activity.
Conclusions:
- The secreted P65 protein of Trichomonas vaginalis functions as an NADP(+)-dependent malic enzyme.
- This enzyme's dual adhesive and catalytic functions suggest a role in the parasite's pathogenetic mechanisms, potentially interacting with pH-dependent perforins.