Purification and Properties of 3-cis-2-trans-Enoyl-CoA Isomerase (Dodecenoyl-CoA Δ-Isomerase) from Rat Liver Mitochondria

: The mitochondrial enzyme 3-cis-2-trans-enoyl-CoA isomerase, responsible for the positional and geometric isomerization of beta,gamma-unsaturated fatty acyl-CoA intermediates arising during beta-oxidation of unsaturated long chain fatty acids, has been isolated from rat liver, purified to homogeneity by a heat step and a combination of gel filtration and ion-exchange chromatographic procedures. The enzyme has a molecular weight of 30,000, as determined by dodecylsulfate polyacrylamide gel electrophoresis. The isomerase has a strong tendency to form a dimer. It elutes from a calibrated Sephadex G-200 column with an apparent Mr = 60000. The basic isoelectric point, pI 9.0-9.2, is due to its high content in basic amino acids. The amino acid composition determined by the ninhydrin and o-phthalaldehyde detection method is presented.