Alternatives to the isomerase-dependent pathway for the beta-oxidation of oleic acid are dispensable in Saccharomyces cerevisiae. Identification of YOR180c/DCI1 encoding peroxisomal delta(3,5)-delta(2,4)-dienoyl-CoA isomerase.
Fatty acids with double bonds at odd-numbered positions such as oleic acid can enter beta-oxidation via a pathway relying solely on the auxiliary enzyme Delta(3)-Delta(2)-enoyl-CoA isomerase, termed the isomerase-dependent pathway. Two novel alternative pathways have recently been postulated to exist in mammals, and these additionally depend on Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase (di-isomerase-dependent) or on Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase and 2,4-dienoyl-CoA reductase (reductase-dependent). We report the identification of the Saccharomyces cerevisiae oleic acid-inducible DCI1 (YOR180c) gene encoding peroxisomal di-isomerase. Enzyme assays conducted on soluble extracts derived from yeast cells overproducing Dci1p using 3,5,8,11,14-eicosapentenoyl-CoA as substrate demonstrated a specific di-isomerase activity of 6 nmol x min(-1) per mg of protein. Similarly enriched extracts from eci1Delta cells lacking peroxisomal 3,2-isomerase additionally contained an intrinsic 3,2-isomerase activity that could generate 3, 5,8,11,14-eicosapentenoyl-CoA from 2,5,8,11,14-eicosapentenoyl-CoA but not metabolize trans-3-hexenoyl-CoA. Amplification of this intrinsic activity replaced Eci1p since it restored growth of the eci1Delta strain on petroselinic acid for which di-isomerase is not required whereas Eci1p is. Heterologous expression in yeast of rat di-isomerase resulted in a peroxisomal protein that was enzymatically active but did not re-establish growth of the eci1Delta mutant on oleic acid. A strain devoid of Dci1p grew on oleic acid to wild-type levels, whereas one lacking both Eci1p and Dci1p grew as poorly as the eci1Delta mutant. Hence, we reasoned that yeast di-isomerase does not additionally represent a physiological 3,2-isomerase and that Dci1p and the postulated alternative pathways in which it is entrained are dispensable for degrading oleic acid.
Gurvitz
A
A
Institut für Biochemie und Molekulare Zellbiologie der Universität Wien and Ludwig Boltzmann-Forschungsstelle für Biochemie, Vienna Biocenter, Dr Bohrgasse 9, A-1030 Wien, Austria.
Mursula
A M
AM
Yagi
A I
AI
Hartig
A
A
Ruis
H
H
Rottensteiner
H
H
Hiltunen
J K
JK
D000214:Acyl Coenzyme A / Q000378:metabolism; D019748:Carbon-Carbon Double Bond Isomerases / Q000096:biosynthesis* / Q000737:chemistry; D004790:Enzyme Induction / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D008830:Microbodies / Q000201:enzymology; D009154:Mutation; D019301:Oleic Acid / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics
D000214:Acyl Coenzyme A; C056949:eicosapentaenoic acid-coenzyme A; D019301:Oleic Acid; D019748:Carbon-Carbon Double Bond Isomerases; C085575:delta(3,5),delta(2,4)-dienoyl-CoA isomerase