Question

Design an experiment that will determine whether oligomycin is an ETC inhibitor or an uncoupling agent.

Answer 1

Ans. -

Oligomycin is an antibiotic that inhibits ATP synthase by blocking its proton channel, which is necessary for oxidative phosphorylation of ADP to ATP. The inhibition of ATP synthesis would also stop electron transport chain. Oxygen consumption stops because oligomycin inhibits ATP synthesis, which is coupled to the activity of the electron-transport chain. Oxygen consumption ceases because Complex IV is inhibited and the entire chain backs up.

Hammes and Hilborn have carried out a steady state kinetic analysis of the activities of both the soluble and mem- brane forms of the mitochondrial ATPase. They noted that in the particulate ATPase oligomycin is a noncompetitive inhibitor with respect to ATP.

Oligomycin prevents the increase in mitochondrial respiration induced by ADP without inhibiting uncoupler stimulated respiration. NADH remains high and NAD+ is too low for the citric acid cycle to operate.

Oligomycin prevents the increase in mitochondrial respiration induced by ADP without inhibiting uncoupler-stimulated respiration. NADH remains high and NAD+ is too low for the citric acid cycle to operate. Although oligomycin was lethally toxic by itself, in the presence of fructose it protected completely against CCCP induced cell killing. In every instance, cell killing was associated with ATP depletion, whereas protection against lethal cell injury was associated with preservation of ATP.