PECI (peroxisomal D3,D2-enoyl-CoA isomerase), also known as DRS1, ACBD2 or HCA88, is a 359 amino acid protein that localizes to the peroxisomal matrix and contains one ACB (acyl-CoA-binding) domain. 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 a range of enoyl-CoA species, playing an important role in the beta-oxidation of unsaturated fatty acids. The gene encoding PECI maps to human chromosome 6, which contains 170 million base pairs and comprises nearly 6% of the human genome.