MECHANISTIC STUDIES ON FATTY ACYL-COA DEHYDROGENASE

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 256  (22) , 1667-1670
Abstract
It was shown that the partial reaction between [pig liver] fatty acyl-CoA dehydrogenase and acyl-CoA substrate is pH-dependent (larger rate constants at basic pH) and shows a biphasic rate profile indicative of formation of an initial charge transfer complex between the C-2 anion of substrate and enzyme. The present investigation indicates that the complete reaction between acyl-CoA and electron transfer flavoprotein shows a pH profile dependent upon ionization of a single basic group with pK.alpha. = 7.7. These facts are consistent with electron transfer which occurs through an obligatory charge transfer complex between the C-2 anion of substrate and oxidized FAD at the enzyme active site. The anion of acetoacetyl-CoA forms a charge transfer complex with enzyme which serves as a model for the putative catalytically active complex mentioned above. Resonance Raman investigation of this acetoacetyl-CoA-enzyme complex indicates that the 1586 cm-1 band is coupled strongly to the charge transfer electronic transition. Since this vibrational band is associated with .nu.C.dbd.N at N-5, C-4a of the flavin ring, it is suggested that electron transfer takes place at this site.