Conversion of palmitate to unsaturated fatty acids differs in a Neurospora crassa mutant with impaired fatty acid synthase activity

The Neurospora crassa cel (fatty acid chain elongation) mutant has impaired fatty acid synthase activity. The cel mutant requires exogenous 16:0 for growth and converts 16:0 to other fatty acids. In contrast to wild‐type N. crassa, which converted only 42% of the exogenous [7,7,8,8‐2H4]16:0 that was incorporated into cell lipids to unsaturated fatty acids, cel converted 72%. In addition, cel contains higher levels of 18:3δ9,12,15 than wild‐type, and synthesizes two fatty acids, 20:2δ11,14 and 20:3δ11,14,17, found at only trace levels in wild‐type. Thus, the Δ15‐desaturase activity and elongation activity on 18‐carbon polyunsaturated fatty acids are higher for cel than wild‐type. This altered metabolism of exogenous 16:0 may be directly due to impaired flux through the endogenous fatty acid biosynthetic pathway, or may result from altered regulation of the synthesis of unsaturated fatty acids in the mutant.