PECI is an enzyme that localized to the peroxisomal matrix and encloses one ACB(acyl-CoA-binding) domain. PECI is expressed abundantly in liver, heart and skeletal muscle. PECI functions to catalyze the isomerization of both 3-cis and 3-trans double bonds into the 2-trans form in an array of enoyl-CoA species. PECI takes part in the beta-oxidation of unsaturated fatty acids.