The steady state concentrations of coenzyme A-SH and coenzyme A thioester, citrate, and isocitrate during tricarboxylate cycle oxidations in rabbit heart mitochondria.
The steady state mitochondrial content of coenzyme A-SH (CoA), acetyl-CoA, succinyl-CoA, and long chain acyl-CoA has been determined during the oxidation of palmitoylcarnitine by rabbit heart mitochondria. Variation of the substrate concentration during ADP-stimulated (state 3) respiration varies the mitochondrial content of long chain acyl-CoA and the rate of O2 uptake, and permits the conclusion that the Km of beta oxidation for intramitochondrial long chain acyl-CoA is approximately 1 nmol/mg of mitochondrial protein. At near saturating concentrations of palmitoylcarnitine, plus L-malate, the addition of ADP causes a decrease in acetyl-CoA, an increase in CoA and succinyl-CoA, and no clear change in long chain acyl-CoA content. These changes reverse upon the depletion of ADP (state 3 leads to 4 transition). Similar changes in CoA, acetyl-CoA, and succinyl-CoA are seen during state 4 leads to 3 leads to 4 transitions with pyruvate plus L-malate and octanoate plus L-malate as substrates. These results suggest a limitation of flux by citrate synthase during the controlled oxidation of these three substrates. The ratio acetyl-CoA/succinyl-CoA was determined not only during state 3 and state 4 oxidation of palmitoylcarnitine plus L-malate and pyruvate plus L-malate, but also during intermediate respiratory states (state 3 1/2) generated by adding glucose and varying amounts of hexokinase. These intermediate states are characterized by a high succinyl-CoA content, relative to either state 3 or state 4, and a suboptimal flux through citrate synthase, estimated either by pyruvate disappearance or by O2 uptake.
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002951:Citrates / Q000378:metabolism*; D002952:Citric Acid Cycle; D003065:Coenzyme A / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007523:Isocitrates / Q000378:metabolism*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D010101:Oxygen Consumption; D011773:Pyruvates / Q000378:metabolism; D011817:Rabbits; D013386:Succinates / Q000378:metabolism
D002951:Citrates; D007523:Isocitrates; D009840:Oligomycins; D011773:Pyruvates; D013386:Succinates; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000244:Adenosine Diphosphate; D000105:Acetyl Coenzyme A; D007770:L-Lactate Dehydrogenase; D007521:Isocitrate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D003065:Coenzyme A