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.