Isomerization of the double bonds of a conjugated fatty acid during beta-oxidation.

The beta-oxidation of an unsaturated fatty acid containing conjugated double bonds at odd-numbered carbon atoms has not previously been studied. It is, therefore, not clear whether, during the beta-oxidation of such an acid, the double bonds will be isomerized by enoyl-CoA isomerase (delta 3 - delta 2-enoyl-CoA isomerase) with the loss or retention of its conjugated nature. To investigate the problem, (E,E)-3,5-octadienoyl-CoA was synthesized for use as a model substrate, and enoyl-CoA isomerase was partially purified from bovine liver. The isomerization was followed by spectrophotometric and gas liquid chromatographic methods, and the results suggested that the isomerization of the model substrate proceeded with retention of a conjugated double bond system. It is, therefore, proposed that the beta-oxidation intermediate of alpha-eleostearic acid (delta 9,11,13 fatty acid) will also isomerize with retention of the conjugated double bond system.