Converts 3,5-dienoyl-CoAs to the corresponding 2,4-dienoyl-CoAs. Involved in fatty acid metabolism. Required for ECI1 to be peroxisomal located. Lipid metabolism; fatty acid beta-oxidation. Interacts with ECI1. By oleate, through the binding of the OAF1-PIP2 transcriptional activator complex to its promoter ORE element. Expression is also induced during ammonia pulses in yeast colonies, at the beginning of detectable ammonia production. Belongs to the enoyl-CoA hydratase/isomerase family.