The purification and properties of butyryl-coenzyme A dehydrogenase from Peptostreptococcus elsdenii

Butyryl-CoA dehydrogenase prepared by a simple procedure from Peptostreptococcus elsdenii has a molecular weight of approx. 150000. The enzyme has FAD as its prosthetic group. The amino acid analysis is reported. This enzyme, like most of the corresponding mammalian ones, is green. The absorption band at 710nm can be abolished irreversibly by dithionite reduction and air reoxidation; it can be abolished reversibly by phenylmercuric acetate or potassium bromide. The enzyme as isolated appears to be a mixture of a green and a yellow form, both of which are active. This view is supported by the variable ;greenness' of different preparations and the biphasic curve obtained in anaerobic spectrophotometric titrations with dithionite. It can be calculated from the titration results that fully green enzyme would have a peak-to-peak absorption ratio (E(710)/E(430)) as great as 0.54. The green form is much less rapidly reduced by dithionite than the yellow form, but is nevertheless much more readily reduced by dithionite than the enzyme from pig liver. It is also more readily reoxidized by air and shows less tendency to form a semiquinone. Treatment with sodium borohydride produces an unusual reduced species that is probably the 3,4-dihydroflavin.