title: Stabilization of the red semiquinone form of pig kidney general acyl-CoA dehydrogenase by acyl coenzyme A derivatives.
abstract: Pig kidney general acyl-CoA dehydrogenases forms the blue neutral radical on dithionite or photochemical reduction (Thorpe, C., Matthews, R. G., & Williams, C. H. (1979) Biochemistry 18, 331-337] in accord with its classification as a flavoprotein dehydrogenase. However, dithionite reduction of the enzyme in the presence of crotonyl coenzyme A (crotonyl-CoA) or octenoyl-CoA generates the red radical anion as the predominant species at pH 7.6. Crotonyl-CoA binds preferentially to the red radical form, depressing the apparent pK by at least 2.5 pH units to a value of 7.3. Butyryl-, octanoyl-, and palmitoyl-CoA induce very similar spectral changes to those induced by enoyl-CoA derivatives when added anaerobically to the blue semiquinone enzyme. In contrast, the competitive inhibitors acetoacetyl-CoA and heptadecyl-SCoA do not markedly perturb the spectrum of the neutral flavosemiquinone species. The stability of the enzyme radical complexes with either crotonyl- or octanoyl-CoA suggests that there is not effective intraflavin transfer of reducing equivalents between subunits. Perturbation of the spectrum of the one-electron-reduced enzyme by ligands may complicate interpretation of the reaction enzyme by ligands may complicate interpretation of the reaction between substrate complexes of the general acyl-CoA dehydrogenase and electron-transferring flavoprotein.
mesh_terms: D000214:Acyl Coenzyme A; D044944:Acyl-CoA Dehydrogenases / Q000378:metabolism*; D000818:Animals; D004227:Dithionite; D004355:Drug Stability; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D011485:Protein Binding; D011809:Quinones; D013053:Spectrophotometry; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013552:Swine
chemical_list: D000214:Acyl Coenzyme A; D011809:Quinones; D004227:Dithionite; D044944:Acyl-CoA Dehydrogenases