A Possible Role of the Na+/K+-ATPase for O2 Production from H2O2

Abstract

We are attempting to supply a new insight on interaction between Na+/K+-ATPase and H2O2. We demonstrate that in vitro the Na+/K+-ATPase, a non heme-protein, is able to disproportionate H2O2 catalatically into dioxygen and water, as well as C40 catalase. By polarography, we quantify O2 production and by Raman spectroscopy H2O2 consumption. A comparative analysis of kinetics parameters relative to O2 production shows that for Na+/K+-ATPase the affinity of the catalytic site able to transform H2O2 into O2 is twice weaker than that for C40 catalase. It also shows that the molar activity for O2 production is 300-fold weaker for ATPase than for catalase. Inhibitors, pH and GSH studies highlight the differences between the heme- and nonheme-proteins. Indeed, for C40, NaN3 is strongly inhibiting, but much less for ATPase. The pH range for the catalatic activity of ATPase is wide (6.5 to 8.5), while it is not for C40 catalase (optimum at pH 8). The Na+/K+-ATPase catalatic activity is reduced in presence of glutathione, while it is not the case with C40 catalase.