Catalytic properties of the ATPase on submitochondrial particles after exchange of tightly bound nucleotides under different steady state conditions.

Energized submitochondrial particles were subjected to high or low [3H]ATP/[3H]ADP ratios, maintained during steady state by a pyruvate kinase or hexokinase regenerating system, respectively. Under both steady state conditions, about 1.4 mol [3H]nucleotide/mol ATPase was retained but considerably more [3H]ATP was retained with the high [3H]ATP/[3H]ADP ratio. The ATPase activity and the oxygen exchange of these differentially labeled SMP were the same, suggesting a lack of control function of non-catalytic tightly bound nucleotides.