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J Eukaryot Microbiol. 2018 Jan;65(1):70-76. doi: 10.1111/jeu.12435. Epub 2017 Jul 10.

The Non-Canonical Substrates of Trypanosoma cruzi Tyrosine and Aspartate Aminotransferases: Branched-Chain Amino Acids.

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Laboratory of Biochemistry of Tryps - LaBTryps, Instituto de Ciencias Biomédicas, Universidade de Sao Paulo USP, Avenida Professor Lineu Prestes, 1374, Cidade Universitaria, São Paulo, Brasil.
IQUIFIB (CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires), Junin 956, Buenos Aires, 1113, Argentina.


Trypanosoma cruzi, the etiological agent of Chagas disease, lacks genes that encode canonical branched-chain aminotransferases. However, early studies showed that when epimastigotes were grown in the presence of 14 C1 -DL-leucine, the label was incorporated into various intermediates. More recently, our studies provided evidence that T. cruzi epimastigotes display a single ATP-dependent and saturable transport system that enables epimastigotes to uptake branched-chain amino acids (BCAAs) from the culture media. To extend our knowledge of the first step of BCAA catabolism, the ability of this parasite's noncanonical broad specificity aminotransferases, such as tyrosine aminotransferase (TAT) and aspartate aminotransferase (ASAT), to transaminate these amino acids was investigated. Indeed, our results show that TAT and ASAT utilize BCAAs as substrates; however, both enzymes differ in their catalytic competence in utilizing these amino donors. For instance, ASAT transaminates isoleucine nearly 10-fold more efficiently than does TAT. This unique characteristic of TAT and ASAT allows to explain how BCAAs can be oxidized in the absence of a BCAA transaminase in T. cruzi.


Metabolism; tyrosine aminotransferase and aspartate amino transferase


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