Able to isomerize both 3-cis and 3-trans double bonds into the 2-trans form in a range of enoyl-CoA species. Has a preference for 3-trans substrates. a (3Z)-enoyl-CoA = a 4-saturated (2E)-enoyl-CoA a (3E)-enoyl-CoA = a 4-saturated (2E)-enoyl-CoA (2E)-tetradecenoyl-CoA = (3Z)-tetradecenoyl-CoA (3E)-tetradecenoyl-CoA = (2E)-tetradecenoyl-CoA (3E)-octenoyl-CoA = (2E)-octenoyl-CoA (3Z)-octenoyl-CoA = (2E)-octenoyl-CoA (3E)-nonenoyl-CoA = (2E)-nonenoyl-CoA kcat are 100 sec(-1), 210 sec(-1), 540 sec(-1), 58 sec(-1), 47 sec(-1) and 210 sec(-1) for (3Z)-hexenoyl-CoA, (3Z)-octenoyl-CoA, (3Z)-tetradecenoyl-CoA, (3E)-hexenoyl-CoA, (3E)-octenoyl-CoA and (3E)-tetradecenoyl-CoA, respectively. Lipid metabolism; fatty acid beta-oxidation. Additional isoforms may exist. Liver (at protein level). In the C-terminal section; belongs to the enoyl-CoA hydratase/isomerase family.