Glutathionylation of the alpha-subunit of Na,K-ATPase from rat heart by oxidized glutathione inhibits the enzyme

A partially purified Na,K-ATPase preparation from rat heart containing alpha 1- and alpha 2-isoforms of the enzyme was shown to include both subunits in S-glutathionylated state. Glutathionylation of the alpha 1-subunit (but not of the alpha 2-subunit) was partially removed when the preparation was isolated in the presence of dithiothreitol. The addition of oxidized glutathione irreversibly inhibited both isoforms. Inhibition of the enzyme containing the alpha 1-subunit was biphasic, and the rate constants of the inhibition were 3745 +/- 360 and 246 +/- 18 M-1 center dot min(-1). ATP, ADP, and AMP protected the Na,K-ATPase against inactivation by oxidized glutathione.