Pathways for fatty acid elongation and desaturation in Neurospora crassa

Neurospora crassa incorporated exogenous deuterated palmitate (16:0) and C-14-labeled oleate (18:1(Delta 9)) into cell lipids. Of the exogenous 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 unsaturated fatty acids in phospholipid and triacylglycerol is 12 times greater than the mass of 18:0. Deuterium label incorporation in unsaturated fatty acids is only twofold greater than in 18:0, indicating a sixfold 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 Neurospora.