Evidence for a modified pathway of linoleate degradation. Metabolism of 2,4-decadienoyl coenzyme A.

The enzymatic degradation of 2,4-decadienoyl-CoA, an assumed metabolite of linoleic acid, was studied in vitro. 2-trans,4-trans-Decadienoyl-CoA, a metabolite of unsaturated fatty acids with trans double bonds, was readily degraded by a beta-oxidation system reconstituted from purified enzymes, as well as by rat heart mitochondria. In contrast, a mixture of 2-cis,4-cis-decadienoyl-CoA and 2-trans,4-cis-decadienoyl-CoA, the latter of which is assumed to be a metabolite of linoleic acid, was acted upon neither by the reconstituted beta-oxidation system nor by the beta-oxidation system present in rat heart mitochondria. However, all three 2,4-decadienoyl-CoA isomers were rapidly reduced by the NADPH-dependent 2,4-dienoyl-CoA reductase of rat heart mitochondria. Based on these observations, we conclude that 2-trans,4-cis-decadienoyl-CoA, a metabolite of linoleic acid, is not directly degraded via the beta-oxidation cycle, but instead is reduced by the NADPH-dependent 2,4-dienoyl-CoA reductase to 3-decenoyl-CoA which is further degraded via the beta-oxidation pathway.