Effect of ATP on the activity of bovine heart mitochondrial b-c1 complex

The effect of ATP on the reductase activity of purified bovine heart b-c1 complex was studied. ATP stimulates the steady-state activity and the antimycin-insensitive pre-steady-state reduction of b and c1 cytochromes, also causing changes of kinetic properties of the enzyme. There is no absolute specificity for ATP since other polyvalent anions such as EDTA and EGTA produce similar effects in the micromolar range. It is proposed that ATP stimulates the activity of the b-c1 complex, chelating inhibitory cation(s), exerting a modulatory action on the enzyme.