PATHWAYS FOR FATTY-ACID ELONGATION AND DESATURATION IN NEUROSPORA-CRASSA

Neurospora crassa incorporated exogenous deuterated palmitate (16:0) a nd C-14-labeled oleate (18:1(Delta 9)) into cell lipids. Of the exogen ous 18:1(Delta 9) incorporated, 59% was desaturated to 18:2(Delta 9,12 ) and 18:3(Delta 9,12,15). Of the exogenous 16:0 incorporated, 20% was elongated to 18:0, while 37% was elongated and desaturated into 18:1( Delta 9), 18:2(Delta 9,12), and 18:3(Delta 9,12,15). The mass of unsat urated fatty acids in phospholipid and triacylglycerol is 12 times gre ater than the mass of 18:0. Deuterium label incorporation in unsaturat ed fatty acids is only twofold greater than in 18:0, indicating a sixf old preferential use of 16:0 for saturated fatty acid synthesis. These results indicate that the release of 16:0 from fatty acid synthase is a key control point that influences fatty acid composition in Neurosp ora.