(Na+ + K+)-ATPase: inactivation and degradation induced by oxygen radicals.

1. Purified (Na+ + K+)-ATPase was irreversibly inhibited upon exposure to hydrogen peroxide, the superoxide anion, and the hydroxyl radical. 2. Comparison of the SDS-gel electrophoretic patterns of the ATPase samples exposed to these oxidants revealed that inhibition occurred either without gross structural changes, or concomitant with fragmentation and cross-linking of the enzyme subunits. 3. The oxidant modified ATPase was also shown to be more susceptible to degradation by several proteolytic enzymes.