Nutritional regulation of yeast delta-9 fatty acid desaturase activity.
The addition of unsaturated fatty acids to cultures of Saccharomyces cerevisiae significantly altered the microsomal lipid composition. Supplementation with either of the naturally occurring palmitoleic (16:1) or oleic (18:1) acids caused increased levels in membrane phospholipids and reduced levels of the complementary acid. Growth in the presence of equimolar quantities of 16:1 and 18:1 acids, however, produced a fatty acid composition similar to that found in unsupplemented cell membranes. Linoleic acid (18:2) was not found in S. cerevisiae grown under normal conditions. It was preferentially internalized and incorporated into microsomes, however, at levels exceeding 50% of the total fatty acid species. This resulted in an almost total loss of 16:1 and a reduction of 18:1 to 25% of its normal level. The delta-9 fatty acid desaturase, a microsomal enzyme that forms 16:1 and 18:1 from saturated acyl coenzyme A precursors, was affected by the presence of exogenous fatty acids. Enzyme activity toward the 16:0 coenzyme A substrate was elevated in microsomes from saturated-fatty-acid-supplemented cultures and sharply repressed following the addition of unsaturated fatty acids, including 18:2. Northern (RNA blot) and slot-blot analyses of mRNA encoded by the OLE1 gene, which appears to be the structural gene for the delta-9 desaturase, indicated that it was sharply reduced in unsaturated-fatty-acid-fed cells. These data suggest that a significant part of the regulation involves modulation of available transcripts.
Bossie
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MA
Bureau of Biological Research, Nelson Laboratories, Rutgers University, Piscataway, New Jersey 08855-1059.
Martin
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CE
D015152:Blotting, Northern; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008861:Microsomes / Q000201:enzymology; D012331:RNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D013230:Stearoyl-CoA Desaturase; D013329:Structure-Activity Relationship
D005231:Fatty Acids, Unsaturated; D012331:RNA, Fungal; D012333:RNA, Messenger; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; C029627:delta-9 fatty acid desaturase