EFFECT OF NITROSO-COMPOUNDS ON NA K-ATPASE

Thiol containing NO.-derivatives were found to inhibit the activity of brain and kidney Na/K-ATPase. S-Nitrosogluthatione demonstrated only minor inhibiting activity, while dinitrosyl iron complexes (DNIC) with cysteine or glutathione were much more effective. Brain Na/K-ATPase i s more vulnerable to inhibiting action than kidney Na/K-ATPase. Inhibi tion of the activity is accompanied by a decrease in amount of protein thiol groups and a change in the substrate dependence curve of the en zyme, Restoration of Na/K-ATPase activity by SH-reagent dithiothreitol or cysteine is accompanied by restoration of SH-groups of the enzyme. This suggests that blockade of SH-groups of Na/K-ATPase is responsibl e for the inhibition. The possibility that this blockade results in di sordering of interprotomer interactions within the oligomeric complexe s of Na/K-ATPase is suggested. Possible regulatory meaning of the effe ct of NO. derivatives is discussed. (C) 1997 Elsevier Science B.V.