PURIFICATION AND CHARACTERIZATION OF A PLANT PEROXISOMAL DELTA-2-ENOYL-COA, DELTA-3-ENOYL-COA ISOMERASE ACTING ON 3-CIS-ENOYL-COA AND 3-TRANS-ENOYL-COA

A DELTA-3,DELTA-2-enoyl-CoA isomerase was extracted from fat-degrading cotyledons of cucumber seedlings. The enzyme is required for the degradation of cis-unsaturated fatty acids, e.g. linoleic acid being present in the storage tissue of cucumber seedlings in high amounts. The DELTA-2,DELTA-3-enoyl-CoA isomerase was exclusively localized within peroxisomes. Its purification included chromatography on a hydrophobic matrix, a cation exchanger, and on hydroxylapatite. 17 000-fold purification yielded a protein of apparent homogeneity. The isomerase is a homodimer with a M(r) of 50 000 and an isoeletric point of pH approximately 8.1. DELTA-3,DELTA-2-Enoyl-CoA isomerase reversibly catalyzes the conversion of both cis-3-enoyl-CoA and trans-3-enoyl-CoA into trans-2-enoyl-CoA. The isomerase exhibited optimal activity at pH 9 and was active with 3-enoyl-CoA species having chain lengths of C6-C-12, with cis-hexenoyl-CoA being the most effective substrate. The purified enzyme did not show enoyl-CoA hydratase activity.