Structural modulation of 2-enoyl-CoA bound to reduced acyl-CoA dehydrogenases: a resonance Raman study of a catalytic intermediate.
A catalytic intermediate, the so-called "purple complex," of acyl-CoA dehydrogenase is produced on its reaction with the substrate, acyl-CoA. The purple complex is a charge-transfer complex between the reduced enzyme and the product, enoyl-CoA. Resonance Raman spectra of the purple complexes of three acyl-CoA dehydrogenases [short-chain acyl-CoA (SCAD), medium-chain acyl-CoA (MCAD), and isovaleryl-CoA (IVD) dehydrogenases] were measured with excitation at 632.8 nm within charge-transfer absorption bands. The 1,577 cm-1 band of the SCAD purple complex formed in the reaction with butyryl-CoA is mainly associated with the C(1) = O stretching of crotonyl-CoA, judging from the isotopic frequency shifts upon 13C or 18O substitution of butyryl-CoA. The 1,627 cm-1 band of the C(1) = O moiety of crotonyl-CoA in solution shifted downward by 50 cm-1 on complexation with reduced SCAD. This large frequency shift indicates a substantial interaction between C(1) = O and the enzyme, and is further evidence for an appreciable contribution of a polarized form of the C(1) = O moiety in the enzyme-bound enoyl-CoA. This frequency shift can be explained by the hydrogen bond of C(1) = O. The 1,577 cm-1 band of the MCAD purple complex remained constant, regardless of the acyl carbon-chain length (from C4 to C16 of the substrate, acyl-CoA); the alky chain scarcely affected the interaction of the C(1) = O moiety in the active site.(ABSTRACT TRUNCATED AT 250 WORDS)
Nishina
Y
Y
Department of Physiology, Kumamoto University School of Medicine.
Sato
K
K
Hazekawa
I
I
Shiga
K
K
D000214:Acyl Coenzyme A / Q000737:chemistry* / Q000378:metabolism*; D042964:Acyl-CoA Dehydrogenase; D044944:Acyl-CoA Dehydrogenases / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D010084:Oxidation-Reduction; D012996:Solutions; D013059:Spectrum Analysis, Raman; D013552:Swine
D000214:Acyl Coenzyme A; D012996:Solutions; C024343:butyryl-coenzyme A; C017447:isovaleryl-coenzyme A; C010701:crotonyl-coenzyme A; D044944:Acyl-CoA Dehydrogenases; D042964:Acyl-CoA Dehydrogenase