Cation-activated ATPase activity of plasmalemma-enriched membrane preparations from maize coleoptiles

The ATPase activity present in plasmalemma-enriched preparations from maize coleoptiles shows an optimum at pH 6, a strong dependence on Mg(2+), and is stimulated by K(+) and other monovalent cations, both organic and inorganic. The activation of ATPase by K(+) obeys Michaelis Menten kinetics, saturation being reached at 50 mM K(+) concentration. K(+), Mg(2+)-stimulated ATPase activity is strongly inhibited by N,N'-dicyclohexylcarbodiimide and by diethylstilbestrol and, to a lesser extent, by octylguanidine.