Isomerization of 3-trans,5-cis-dienoyl-CoA to 2-trans,4-trans-dienoyl-CoA. (3E,5Z)-octadienoyl-CoA = (2E,4E)-octadienoyl-CoA (3E,5Z,8Z,11Z,14Z)-eicosapentaenoyl-CoA = (2E,4E,8Z,11Z,14Z)-eicosapentaenoyl-CoA Lipid metabolism; fatty acid beta-oxidation. Homohexamer. Expressed in heart and liver (at protein level). Belongs to the enoyl-CoA hydratase/isomerase family.