Studies with general acyl-CoA dehydrogenase from pig kidney. Inactivation by a novel type of "suicide" inhibitor, 3,4-pentadienoyl-CoA.
3,4-Pentadienoyl-CoA, an allenic substrate analog, is a potent inhibitor of the flavoprotein pig-kidney general acyl-CoA dehydrogenase. The analog reacts very rapidly (k = 2.4 X 10(3) min-1) with the native oxidized enzyme to form a covalent flavin adduct probably involving the isoalloxazine position N-5. This species is inactive, but activity may be regained by two pathways. The allenic thioester can be displaced (k = 0.3 min-1) by a large excess of octanoyl-CoA substrate upon reversal of covalent adduct formation. Alternatively, the enzyme inactivator adduct slowly decomposes (t1/2 = 75 min) to form the strongly thermodynamically favoured 2,4-diene and catalytically active, oxidized enzyme. During this latter process 15-20% of the activity is irreversibly lost probably due to covalent modification of the protein. These data suggest that 3,4-pentadienoyl-CoA should be considered a suicide substrate of the acyl-CoA dehydrogenase. The mechanism of the reactions, and in particular the 3,4----2,4 tautomerization, are consistent with a catalytic sequence initiated by abstraction of an alpha-hydrogen as a proton.
D000214:Acyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology*; D044944:Acyl-CoA Dehydrogenases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D005415:Flavins / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D013552:Swine
D000214:Acyl Coenzyme A; D005415:Flavins; C044771:3,4-pentadienoyl-coenzyme A; D044944:Acyl-CoA Dehydrogenases