Delta(3,5,7),Delta(2,4,6)-trienoyl-CoA isomerase, a novel enzyme that functions in the beta-oxidation of polyunsaturated fatty acids with conjugated double bonds

The mitochondrial metabolism of unsaturated fatty acids with conjugated dou ble bonds at odd-numbered positions, e.g. 9-cis,11-trans-octadecadienoic ac id, was investigated. These fatty acids are substrates of beta-oxidation in isolated rat liver mitochondria and hence are expected to yield 5,7-dienoy l-CoA intermediates. 5,7-Decadienoyl-CoA was used to study the degradation of these intermediates. After introduction of a 2-trans-double bond by acyl -CoA dehydrogenase or acyl-CoA oxidase, the resultant 2,5,7-decatrienoyl-Co A can either continue its pass through the beta-oxidation cycle or be conve rted by Delta(3),Delta(2)-enoyl-CoA isomerase to 3,5,7-decatrienoyl-CoA. Th e latter compound was isomerized by a novel enzyme, named Delta(3,5,7),Delt a(2,4,6)-trienoyl-CoA isomerase, to 2,4,6-decadrienoyl-CoA, which is a subs trate of 2,4-dienoyl-CoA reductase (Wang, H.-Y. and Schulz, I-I. (1989) Bio chem, J. 264, 47-52) and hence can be completely degraded via beta-oxidatio n. Delta(3,5,7),Delta(2,4,6)-Trienoyl-CoA isomerase was purified from pig h eart to apparent homogeneity and found to be a component enzyme of Delta(3, 5),Delta(2,4)-dienoyl-CoA isomerase. Although the direct beta-oxidation of 2,5,7-decatrienoyl-CoA seems to be the major pathway, the degradation via 2 ,4,6-trienoyl-CoA makes a significant contribution to the total beta-oxidat ion of this intermediate.