Initial observations on the role of glutathione peroxidases in Euglena

The algae Euglena gracilis possesses two glutathione (GSH) peroxidase: a GSH peroxidase that reduces organic hydroperoxides as well as hydrogen peroxide (GSH peroxidase 1); and a GSH peroxidase associated with GSH transferase that is active only with organic hydroperoxide substrates (GSH peroxidase 2). Preliminary experiments with Euglena were conducted to explore the in vivo role of the GSH peroxidases. The enzymes were not induced in response to the stimulation of cellular processes that generate oxidant species, such as β-oxidation or photosynthesis. The levels of GSH peroxidase 1 were approximately twofold higher in autotrophic cultures containing the herbicide DCMU. GSH peroxidase 1 was most active in stationary phase cells; while the levels of GSH peroxidase 2 were fairly constant throughout growth. Under conditions where lipid peroxidation was induced in Euglena, the addition of either GSH peroxidase plus GSH reduced the lipid peroxide levels more than tenfold.