Effect of bicarbonate and other anions on the oxidized and reduced forms of F1-ATPase.

The effect of activating anions on the hydrolysis of ATP catalyzed by mitochondrial ATPase was higher on the oxidized than on the reduced form of the enzyme. On the contrary the effect of inhibitory anions on this reaction was more manifest on the reduced form of the enzyme. Kinetic data show that both activating and inhibitory anions compete for the same sites of the ATPase. A unifying mechanism of action is suggested according to which the anions could establish coordination bonds with the suggested iron atoms of the catalytic site. The preferential displacement of electrons of such bonds towards the ligand, or towards the metal atom, would lead respectively to an inhibition or to an activation of the enzyme.