New enzymatic pathways for the reduction of reactive oxygen species in Entamoeba histolytica

CABEZA, MS; GUERRERO, SA; IGLESIAS, AA; ARIAS, DG

BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS

ELSEVIER SCIENCE BV

Lugar: Amsterdam ; Año: 2015 vol. 1850 p. 1233 - 1244

0304-4165

Background Entamoeba histolytica, an intestinal parasite that is the causative agent of amoebiasis, is exposed to elevated amounts of highly toxic reactive oxygen and nitrogen species during tissue invasion. Recently it has been characterized in this human pathogen a flavodiiron protein and a rubrerythrin, but no physiological reductants have been identified. Methods The present work deals with biochemical studies aimed to reach a better understanding of the kinetic and structural properties of an amebic rubredoxin reductase and two ferredoxins from E. histolytica. Results We have complemented the characterization in E. histolytica of two different metabolic pathways for O2 and H2O2 detoxification. We characterized a novel amebic protein with rubredoxin reductase activity that is able to catalyze the NAD(P)H-dependent reduction of heterologous rubredoxins, amoebic rubrerythrin and flavodiiron protein but not ferredoxins. In addition, this enzyme exhibited NAD(P)H oxidase activity, which generates hydrogen peroxide from molecular oxygen. Additionally, we described how different ferredoxins were also efficient as reductant substrate for flavodiiron protein and rubrerythrin. Conclusions and General Significance These proteins could contribute to O2 and H2O2 detoxification as two alternative systems in vivo, playing an important role in the parasite defense against reactive oxidant species. So far we know this is the first characterization of eukaryotic NROR protein (from E. histolytica) and the first kinetic study of ferredoxin-dependent reduction of flavodiiron protein and rubrerythrin.