ECI2 in the peroxisome matrix catalyzes the isomerizeation of 3Z-enoyl-CoA to 2E-enoyl-CoA. The active form of the enzyme is a homotrimer (Onwukwe et al. 2015). The reaction annotated here, involving octenoyl-CoA isomers is the one originally characterized by Geisbreacht et al. (1999), although the enzyme is active on enoyl-CoAs of a range of chain lengths.