(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.
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Research Article|
September 01 1974
The control of tricarboxylate-cycle 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
Richard G. Hansford
Richard G. Hansford
1Laboratory of Molecular Aging, Gerontology Research Center, National Institute of Child Health and Human Development, National Institutes of Health, Baltimore City Hospitals, Baltimore, Md. 21224, U.S.A.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1974 London: The Biochemical Society
1974
Biochem J (1974) 142 (3): 509–519.
Citation
Richard G. Hansford; The control of tricarboxylate-cycle 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. Biochem J 1 September 1974; 142 (3): 509–519. doi: https://doi.org/10.1042/bj1420509
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