A possible role of the Na+/K+-ATPase for O-2 production from H2O2

We are attempting to supply a new insight on interaction between Na+/K+-ATP ase and H2O2. We demonstrate that in vitro the Na+/K+-ATPase, a non hemepro tein, is able to disproportionate H2O2 catalatically into dioxygen and wate r, as well as C-40 catalase. By polarography, we quantify O-2 production an d by Raman spectroscopy H2O2 consumption. A comparative analysis of kinetic s parameters relative to O-2 production shows that for Na+/K+-ATPase the af finity of the catalytic site able to transform H2O2 into O-2 is twice weake r than that for C-40 catalase. It also shows that the molar activity for O- 2 production is 300-fold weaker for ATPase than for catalase. Inhibitors, p H and GSH studies highlight the differences between the heme-and nonheme-pr oteins. Indeed, for C-40, NaN3 is strongly inhibiting, but much less for AT Pase. The pH range for the catalatic activity of ATPase is wide (6.5 to 8.5 ), while it is not for C-40 catalase (optimum at pH 8). The Na+/K+-ATPase c atalatic activity is reduced in presence of glutathione, while it is not th e case with C40 catalase. (C) 2000 Academic Press.