title: The control of tricarboxylate-cycle of oxidations in blowfly flight muscle. The steady-state concentrations of coenzyme A, acetyl-coenzyme A and succinyl-coenzyme A in flight muscle and isolated mitochondria.
abstract: (1) A ;cycling' method involving citrate synthase (EC 4.1.3.7) and malate dehydrogenase (EC 1.1.1.37) was modified by the inclusion of succinyl-CoA synthetase (EC 6.2.1.5) and hexokinase (EC 2.7.1.1) to permit the determination of very small amounts of succinyl-CoA in addition to CoA and acetyl-CoA. (2) Application of this technique to blowfly (Phormia regina) flight-muscle extracts reveals no change in acetyl-CoA concentration, a slight fall in CoA concentration and a rise in succinyl-CoA concentration during flight. (3) Extraction of isolated mitochondria during controlled (state 4) pyruvate oxidation reveals essentially only acetyl-CoA. Activation of respiration by ADP (state 3) or uncoupling agents leads to a fall in acetyl-CoA and a rise in CoA and succinyl-CoA content. (4) The presence of glycerol phosphate in addition to pyruvate results in a lower acetyl-CoA content in state 4. (5) It is contended that these results are consistent with a primary control of one of the reactions of the tricarboxylate cycle, rather than of pyruvate dehydrogenase, during the state 4 oxidation of pyruvate by isolated mitochondria, and that the modulation of citrate synthase activity by the ratio of acetyl-CoA/succinyl-CoA is unimportant under these conditions.
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D002952:Citric Acid Cycle; D003065:Coenzyme A / Q000031:analogs & derivatives* / Q000378:metabolism*; D003066:Coenzyme A Ligases / Q000378:metabolism; D004175:Diptera / Q000378:metabolism*; D005260:Female; D005426:Flight, Animal; D006593:Hexokinase / Q000378:metabolism; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption; D011773:Pyruvates / Q000494:pharmacology; D013386:Succinates; D013997:Time Factors
chemical_list: D011773:Pyruvates; D013386:Succinates; D000105:Acetyl Coenzyme A; D008291:Malate Dehydrogenase; D002950:Citrate (si)-Synthase; D006593:Hexokinase; D003066:Coenzyme A Ligases; D003065:Coenzyme A