Long chain polyunsaturated fatty acid synthesis in a marine vertebrate: Ontogenetic and nutritional regulation of a fatty acyl desaturase with Δ4 activity

► We functionally characterized a fatty acyl desaturase and elongase in sole. ► Fad has Δ4-activity and Elovl has substrate specificity typical of fish Elovl5. ► Sole appears able to synthesize DHA from EPA via a Sprecher-independent pathway. ► Δ4fad and elovl5 showed a marked pattern of regulation during early ontogenesis. ► Δ4fad shows nutritional regulation, up-regulated in response to LC-PUFA-poor diets.