Purification and properties of rat liver acyl-CoA dehydrogenases and electron transfer flavoprotein

Three acyl-CoA dehydrogenases and electron transfer flavoprotein, which catalyze the initial step of mitochondrial fatty acid beta-oxidation, were purified from livers of rats fed a diet containing di(2-ethylhexyl)phthalate. Three acyl-CoA dehydrogenases, classified into short chain, general, and long chain acyl-CoA dehydrogenases on the basis of their substrate specificities, each consisted of four subunits of identical size: the molecular weights of the native enzymes were 169,000 for short chain acyl-CoA dehydrogenase, 182,000 for general acyl-CoA dehydrogenase, and 168,000 for long chain acyl-CoA dehydrogenase. Electron transfer flavoprotein with a molecular weight of 57,000 consisted of heterogeneous subunits with molecular weight of 33,500 and 25,100. The catalytic properties and molecular structures of rat liver acyl-CoA dehydrogenases were similar to those of the enzymes purified from other mammalian tissues such as pig heart, pig liver, and beef kidney. We could not obtain purified preparations of the three acyl-CoA dehydrogenases from livers of the control rats although the three dehydrogenases were completely separated from each other. The enzymes from the control and the di(2-ethylhexyl)phthalate-treated rats were compared and no differences were found in molecular sizes of the native enzymes and of their subunits, substrate specificities and immunochemical reactivities.