INIMEC - CONICET   05467
INSTITUTO DE INVESTIGACION MEDICA MERCEDES Y MARTIN FERREYRA
Unidad Ejecutora - UE
artículos
Título:
Immunolocalization and enzymatic functional characterization of the thioredoxin system in Entamoeba histolytica.
Autor/es:
ARIAS DG, CARRANZA PG, LUJAN HD, IGLESIAS AA, GUERRERO SA.
Revista:
FREE RADICAL BIOLOGY AND MEDICINE
Editorial:
Elsevier Inc.
Referencias:
Año: 2008 vol. 45 p. 32 - 39
ISSN:
0891-5849
Resumen:
The components of the redox metabolism in Entamoeba histolytica have been recently revisited by Arias et al.
(Free Radic. Biol. Med. 42:14961505; 2007), after the identification and characterization of a thioredoxinlinked
system. The present work deals with studies performed for a better understanding of the localization
and identification of different components of the redox machinery present in the parasite. The gene encoding
for amoebic thioredoxin 8 was cloned and the recombinant protein typified as having properties similar to
those of thioredoxin 41. The ability of these thioredoxins and the specific reductase to assemble a system
utilizing NADPH to metabolize hydroperoxides in association with a peroxiredoxin has been kinetically
characterized. The peroxiredoxin behaved as a typical 2 cysteine enzyme, exhibiting a ping-pong mechanism
with hyperbolic saturation kinetics for thioredoxin 8 (Km=3.8 ìM), thioredoxin 41 (Km=3.1 ìM), and tert-butyl
hydroperoxide (Km about 35 ìM). Moreover, the tandem system involving thioredoxin reductase and either
thioredoxin proved to be operative for reducing low molecular weight disulfides, including putative
physiological substrates as cystine and oxidized trypanothione. Thioredoxin reductase and thioredoxin 41
(by association also the functional redox system) have been immunolocalized underlying the plasma
membrane in Entamoeba histolytica cells. These findings suggest an important role for the metabolic pathway
involving thioredoxin as a redox interchanger, which could be critical for the maintenance and virulence of the
parasite when exposed to highly toxic reactive oxygen species.