Babesia hylomysci and B. divergens: presence of antioxidant enzymes destroying hydrogen peroxide.

Catalase and glutathione peroxidase (Gpx), two enzymes destroying hydrogen peroxide, were reported in two Babesia species: B. divergens cultivated in vitro and B. hylomysci obtained in vivo. On the use of specific substrate and inhibitor, we confirmed that the Gpx activity detected was selenium-dependent. Moreover, the two Babesia species contain glutamate dehydrogenase activity. This enzyme is capable of providing to the cell the reduced nicotinamide adenine dinucleotide phosphate (NADPH) necessary for regeneration of the reduced glutathione. Gpx activity is weaker in B. divergens than in B. hylomysci and seems to be compensated by higher levels of catalase activity. Such a balance between the two enzymes may depend on the selenium concentration available for the parasite.