Studies on the Substrate Specificity of the Inducible and Non-Inducible Acyl-CoA Oxidases from Rat

We have studied the substrate specificity of the inducible (acyl-CoA oxidase I) and non-inducible (acyl-CoAoxidase II) oxidases in peroxisome-enriched fractions from rat kidney. The two oxidases were separated by means of ion-exchange chromatography and shown 10 accept a variety of acyl-CoA esters as substrates, including lignoceroyl-CoA, palmi1oyl-CoA, lauroyl-CoA, caproyl-CoA, and trimethyltridecanoyl-CoA. Glutaryl-CoA was found 10 react exclusively with the inducible enzyme, and pristanoyl-CoA exclusively with the non-inducible enzyme. We conclude that under normal non-induced conditions both acyl-CoA oxidase I and II contribute to the oxidation of the various acyl-CoA esters with the exception of pristanoyl-CoA and glutaryl-CoA, although the extent 10 which each enzyme contributes to the oxidation was found 10 differ between the various acyl-CoA esters. Mitochondria were long believed to be the sole site of fatty acid j3-oxidation. Following the finding of Lazarow and de Duve (1) that rat liver peroxisomes are also capable of fatty acid j3-oxidation, it has been established that non-mito