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J. Biol. Chem., Vol. 276, Issue 2, 895-903, January 12, 2001

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Peroxisomal Degradation of trans-Unsaturated Fatty Acids in the Yeast Saccharomyces cerevisiae^*

Aner Gurvitz, Barbara Hamilton, Helmut Ruis, and Andreas Hartig

From the Institut für Biochemie und Molekulare Zellbiologie der Universität Wien and Ludwig Boltzmann-Forschungsstelle für Biochemie, Vienna Biocenter, Dr Bohrgasse 9, A-1030 Vienna, Austria

Degradation of trans-unsaturated fatty acids was studied in the yeast Saccharomyces cerevisiae. Propagation of yeast cells on trans-9 elaidic acid medium resulted in transcriptional up-regulation of the SPS19 gene, whose promoter contains an oleate response element. This up-regulation depended on the Pip2p-Oaf1p transcription factor and was accompanied by induction of import-competent peroxisomes. Utilization of trans fatty acids as a single carbon and energy source was evaluated by monitoring the formation of clear zones around cell growth on turbid media containing fatty acids dispersed with Tween 80. For metabolizing odd-numbered trans double bonds, cells required the -oxidation auxiliary enzyme ³-²-enoyl-CoA isomerase Eci1p. Metabolism of the corresponding even-numbered double bonds proceeded in the absence of Sps19p (2,4-dienoyl-CoA reductase) and Dci1p (^3,5-^2,4-dienoyl-CoA isomerase). trans-2,trans-4-Dienoyl-CoAs could enter -oxidation directly via Fox2p (2-enoyl-CoA hydratase 2 and D-specific 3-hydroxyacyl-CoA dehydrogenase) without the involvement of Sps19p, whereas trans-2,cis-4-dienoyl-CoAs could not. This reductase-independent metabolism of trans-2,trans-4-dienoyl-CoAs resembled the situation postulated for mammalian mitochondria in which oleic acid is degraded through a di-isomerase-dependent pathway. In this hypothetical process, trans-2,trans-4-dienoyl-CoA metabolites are generated by ³-²-enoyl-CoA isomerase and ^3,5-^2,4-dienoyl-CoA isomerase and are degraded by 2-enoyl-CoA hydratase 1 in the absence of 2,4-dienoyl-CoA reductase. Growth of a yeast fox2sps19 mutant in which Fox2p was exchanged with rat peroxisomal multifunctional enzyme type 1 on trans-9,trans-12 linolelaidic acid medium gave credence to this theory. We propose an amendment to the current scheme of the carbon flux through -oxidation taking into account the dispensability of -oxidation auxiliary enzymes for metabolizing trans double bonds at even-numbered positions.

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