Thioredoxin reductase from Entamoeba histolytica HK9. Molecular cloning and functional characterization.

ARIAS D; GUTIÉRREZ C; GUERRERO SA; IGLESIAS AA

Pinamar – Argentina

Congreso; SAIB XLI Reunión Anual; 2005

Entamoeba histolytica, an intestinal parasitic protozoan, is the causative agent of amoebiasis. The parasite usually lives and multiplies within the human gut, under reduced oxygen. During tissue invasion, E. histolytica is exposed to elevated amounts (highly toxic) of reactive oxygen species (ROS). Pathway for ROS detoxification in this organism is  controversial. It has been proposed cystein as a main intracellular thiol and one of the compounds responsible for the maintenance of redox balance. In this work we present the cloning of the gene (trxr) coding for thioredoxin reductase (TRXR), from E. histolytica genomic DNA. The gene was cloned into the vector pRSET-A and the construction obtained was used to transform competent cells of Escherichia coli BL21(DE3). The recombinant protein was purified  and functionally characterized by its ability to catalyze the NADPH (S0.5 = 1.3 mM; nH = 3.7) dependent reduction of both, 5,5´-dithiobis-(2-nitrobenzoic) acid (DTNB) (S0.5 = 1.4 mM; nH = 1.2), and TRX from E. coli (S0.5 = 5.6 mM; nH = 1.6). Our results support the occurrence of a TRXR/TRX system in E. histolytica, as a principal component of the parasite redox metabolism.