Oxidative resistance of Na/K-ATPase

1. Oxidative modification of Na/K-ATPase from brain and kidney has been stu died. Brain enzyme has been found to be more sensitive than kidney enzyme t o inhibition by both H2O2 and NaOCl. 2. The inhibition of Na/K-ATPase correlates well with the decrease in a num ber of SH groups, suggesting that the latter belong mainly to ATPase protei n and are essential for the enzyme activity. We suggest that the difference s in the number, location, and accessibility of SH groups in Na/K-ATPase is ozymes predict their oxidative stability. 3. The hydrophilic natural antioxidant carnosine, the hydrophobic natural a ntioxidant alpha-tocopherol, and the synthetic antioxidant ionol as well as the ferrous ion chelating agent deferoxamine were found to protect Na/K-AT Pase from oxidation by different concentrations of H2O2 The data suggest th at these antioxidants are effective due to their ability to neutralize or t o prevent formation of hydroxyl radicals.