The modification of (Na + + K +) ATPase sensitivity to ouabain after extraction of membrane constituents distinct from the enzyme

Abstract

The (Na+ + K+)ATPase from mouse plasmocytoma MOPC 173 ascitic cells was found to be resistant to ouabain in purified plasma membranes as 50 % of the enzyme activity (E 1/2) was inhibited by 120 μM ouabain. After 2 treatments by a sucrose-EDTA-imidazole buffer, the plasma membrane-bound enzyme recovered in the pellet was found to be much more sensitive to ouabain inhibition (E 1/2 = 0,4 μM). The original (Na+ + K+) ATPase sensitivity to ouabain can be restored by addition of concentrated supernatants from EDTA-treated membranes plus Ca++ and Mg++ to the pellet.