Phosphorylating efficiency of isolated rat liver mitochondria respiring under the conditions of steady-State 4.
A limited, but significant net formation of ATP was observed during the very first period of respiratory State 4. The synthesis appeared to depend on respiration, since it was completely inhibited by KCN or by 2,4-dinitrophenol. Accordingly, State 4 respiration was observed to be inhibited to a large extent by oligomycin. After the initial increase, the level of ATP remained unmodified under the conditions of steady-state 4. Also, the maintenance of the equilibrium level of ATP was very sensitive to KCN or 2,4-dinitrophenol. Under the very same conditions of State 4, the mitochondria exhibited a significant ATPase activity, which appeared to be competitively inhibited by ADP. Therefore, it might be concluded that the apparently constant level of ATP observed in State 4 results from a balanced equilibrium between a respiration-dependent synthesis and a continuous hydrolysis. A comparison between the amount of ATP hydrolysed in State 4 and the amount of oxygen consumed under the same conditions indicated that the phosphorylating efficiency of respiring mitochondria in State 4 is as high as in State 3.
D019297:2,4-Dinitrophenol; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004140:Dinitrophenols / Q000494:pharmacology; D007700:Kinetics; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats
D004140:Dinitrophenols; D009840:Oligomycins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D011190:Potassium Cyanide; D019297:2,4-Dinitrophenol