Molecular characterization of Saccharomyces cerevisiae Delta(3),Delta(2)-enoyl-CoA isomerase

We report here the identification of the Saccharomyces cerevisiae peroxisom al Delta(3),Delta(2)-enoyl-CoA isomerase, an enzyme that is essential for t he beta-oxidation of unsaturated fatty acids. The yeast gene YLR284C was id entified in an in silico screen for genes that contain an oleate response e lement, a transcription factor-binding site common to most fatty acid-induc ed genes. Growth on oleic acid resulted in a significant increase in YLR284 C mRNA, demonstrating that it is indeed an oleate-induced gene. The deduced product of YLR284C contains a type 1 peroxisomal targeting signal-like seq uence at its C terminus and localizes to the peroxisome in a PEX8-dependent manner. Removal of YLR284C from the S. cerevisiae genome eliminated growth on oleic acid, but had no effect on peroxisome biogenesis, indicating a ro le for YLR284C in fatty acid metabolism. Cells lacking YLR284C had no detec table Delta(3),Delta(2)-enoyl-CoA isomerase activity, and a bacterially exp ressed form of this protein catalyzed the isomerization of 3-cis-octenoyl-C oA to 2-trans-octenoyl-CoA with a specific activity of 16 units/mg. We conc lude that YLR284C encodes the yeast peroxisomal Delta(3),Delta(2)-enoyl-CoA isomerase and propose a new name, ECI1, to reflect its enoyl-CoA isomerase activity.