Straight-chain enoyl-CoA thioesters from C4 up to at least C16 are processed, although with decreasing catalytic rate. a (3S)-3-hydroxyacyl-CoA = a (2E)-enoyl-CoA + H2O a 4-saturated-(3S)-3-hydroxyacyl-CoA = a (3E)-enoyl-CoA + H2O (3S)-3-hydroxybutanoyl-CoA = (2E)-butenoyl-CoA + H2O 3-hydroxyisovaleryl-CoA = 3-methyl-(2E)-butenoyl-CoA + H2O 3-hydroxypropanoyl-CoA = acryloyl-CoA + H2O 3-hydroxybutanoyl-CoA = (2E)-butenoyl-CoA + H2O Lipid metabolism; fatty acid beta-oxidation. Homohexamer; dimer of trimers. The monomer is folded into a right-handed spiral of four turns, followed by two small domains which are involved in trimerization. Belongs to the enoyl-CoA hydratase/isomerase family.