Authors

Discussion

The Chagas disease (CD) is a zoonosis caused by the flagellate protozoan Trypanosoma cruzi, which is transmitted by insects of the Reduviidae family. The branched chain amino acids (BCAA) (valine (Val), leucine (Leu) and isoleucine (Ile)), are efficiently uptaken by epimastigotes though an ATP dependent single system. As there is no BCAA biosynthesis in the parasite, their intracellular availability depends on the balance between their incorporation and consumption. We demonstrated that parasites incubated with ¹⁴C-U-Leu are able to oxidize it to CO₂. Additionally, it was early suggested that Leu behaved as a negative modulator of the metacyclogenesis, when we submitted epimastigotes to metacyclogenesis assays in the presence of BCAA differentiation was diminished more than 95% for all BCAA. We explored the ability of BCAAs to interfere with the parasite intracellular infection. In the presence of 5 mM Leu, trypomastigote bursting was 67% diminished. As differentiation and intracellular infection are proline (Pro) dependent, we explored the ability of Leu to inhibit the pyrroline-5-carboxylate dehydrogenase. Leu behaved as a non-competitive inhibitor of TcP5CDH (Ki: 3.5 mM). Thus essential processes in the biology of T. cruzi are dependent on the ability of the parasite to accumulate BCAAs. To better understand the dynamic between uptake and consumption of BCAAs we investigated the first steps in their degradation pathway, which is expected to be catalyzed by specific BCAA transaminase, but according to T. cruzi genome databases this enzyme is absent, we explored if, aspartate and tyrosine aminotransferases could be responsible for a non-canonical BCAA aminotransferase activity. Both were able to transfer the amino group from BCAA to a-ketoglutarate. In conclusion, we have demonstrated a connection between BCAA availability, their metabolism (which comprises unique biochemical activities of ASAT and TAT),