Acyl-CoA oxidase from Candida tropicalis

Abstract
Acyl coA oxidase (acyl-CoA oxidase) was isolated in good yield from C. tropicalis pK 233 grown on n-alkanes. Gel filtrations, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and measurement of flavin content suggest that the oxidase is an octamer of MW 75,000 subunits each containing 1 flavin. The oxidase yields the red semiquinone form on dithionite or photochemical reduction, slowly forms an N-5 adduct with 0.16 M sulfite at pH 7.4 and is rapidly reduced by borohydride, forming the 3,4-dihydroflavin isomer. The red flavosemiquinone is only kinetically stabilized with respect to disproportionation in the free enzyme but is thermodynamically stabilized on binding enoyl-CoA derivatives. The enzyme is reduced by butyryl-, octanoyl- and palmitoyl-CoA without formation of prominent long-wavelength bands. Acyl-CoA oxidase and the acyl-CoA dehydrogenases share many similarities in their interaction with CoA derivatives. Both enzymes stabilize the anionic radical on binding enoyl-CoA derivatives, both dehydrogenate 2-oxoheptadecyldethio-CoA but cannot utilize S-heptadecyl-CoA, both form long-wavelength bands with CoA persulfide species and both enzymes are attacked by the suicide substrates 3,4-pentadienoyl-CoA and (methylene-cyclopropyl)acetyl-CoA at the flavin prosthetic group.