Regulation of ATP hydrolase activity of the F0-F1 complex of rat-liver mitochondria during early hepatic regeneration

AbstractSubmitochondrial particles prepared from rat liver in the early phase of hepatic regeneration possess a reduced F1 content with respect to F0 in intact F0F1-H+-ATPase complexes. Analysis of ATP hydrolysis showed a significant difference in both ESMP and isolated F1 with regard to the higher affinity Km values (Km,1) obtained from Eadie-Hofstee plots. Both ESMP and F1 from regenerating rat liver showed much lower apparent Km,1 values (0.04 and 0.03 mM, respectively) than the corresponding controls (0.08 mM for both ESMP and F1). Data presented here show that the residual F1 moieties have an altered kinetic pattern with regard to the competitive inhibitor adenosine 5'-[β,γ-imido]triphospate (K1 ESMP from regenerating rat liver = 0.67 μM, K1 ESMP from control rat liver = 2.03 μM). This difference in affinity for [β,γ-imido]-ATP is also seen in isolated F1(K1 regenerating rat liver = 0.04 μM, K1 control rat liver = 0.22 μM). These data indicate that during the disruptive retrodifferential phase of hepatic regeneration, changes at the level of surviving F1 sectors of the F0-F1 ATPase may play a physiological role in preventing ATP hydrolysis in vivo in the brief period of low ΔμH+, induced by the presence of non-F1-associated F0 proton-conducting pathways