Acyl-CoA oxidase contains two targeting sequences each of which can mediate protein import into peroxisomes.

Acyl-CoA oxidase is a major induced enzyme in peroxisomes of Candida tropicalis grown on fatty acids. The gene, POX4, encoding acyl-CoA oxidase was expressed in vitro, and the resulting polypeptide was imported into purified peroxisomes in a temperature-dependent fashion. Plasmids containing fragments of POX4 were prepared, expressed and the polypeptides tested for import into peroxisomes. We identified two regions of acyl-CoA oxidase (amino acids 1-118 and 309-427) that contained information that specifically targeted fragments of acyl-CoA oxidase to peroxisomes. The corresponding regions of the gene were fused to cDNA encoding the cytosolic enzyme dihydrofolate reductase (DHFR), and the expressed fusion proteins were likewise imported into peroxisomes. DHFR itself neither bound to, nor was imported into peroxisomes. Thus, there are at least two regions of peroxisomal targeting information in the acyl-CoA oxidase gene.