THE SACCHAROMYCES-CEREVISIAE PEROXISOMAL 2,4-DIENOYL-COA REDUCTASE ISENCODED BY THE OLEATE-INDUCIBLE GENE SPS19

beta-Oxidation is compartmentalized in mammals into both mitochondria and peroxisomes. Fatty acids with double bonds at even-numbered positi ons require for their degradation the auxiliary enzyme 2,4-dienoyl-CoA reductase, and at least three isoforms, two mitochondrial and one per oxisomal, exist in the rat. The Saccharomyces cerevisiae Sps19p is 34% similar to the human and rat mitochondrial reductases, and an SPS19 d eleted strain was unable to utilize petroselineate (cis-C-18:1(6)) as the sole carbon source, but remained viable on oleate (cis-C-18:1(9)). Sps19p was purified to homogeneity from oleate-induced cells and the homodimeric enzyme (native molecular weight 69,000) converted 2,4-hexa dienoyl-CoA into 3-hexenoyl-CoA in an NADPH-dependent manner and there fore contained 2,4-dienoyl-CoA reductase activity, Antibodies raised a gainst Sps19p decorated the peroxisomal matrix of oleate-induced cells . SPS19 shares with the sporulation-specific SPS18 a common promoter r egion that contains an oleate response element, This element unidirect ionally regulates transcription of the reductase and is sufficient for oleate induction of a promoterless CYC1-lacZ reporter gene. SPS19 is dispensable for growth and sporulation on solid acetate and oleate med ia, but is essential for these processes to occur on petroselineate.