Fatty acid metabolism in marine fish: Low activity of fatty acyl Δ5 desaturation in gilthead sea bream ( Sparus aurata) cells

• Published in: Lipids
• Main Authors: Tocher, Douglas R., Ghioni, Cristina
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1999
• Subjects: Turbot
• Online Access: http://dx.doi.org/10.1007/s11745-999-0382-8; https://onlinelibrary.wiley.com/doi/full/10.1007/s11745-999-0382-8

Abstract Marine fish have an absolute dietary requirement for C 20 and C 22 highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in marine fish was either a deficiency in fatty acyl Δ5 desaturase or C 18–20 elongase activity. Recent research in turbot cells found low C 18–20 elongase but high Δ5 desaturase activity. In the present study, the fatty acid desaturase/elongase pathway was investigated in a cell line (SAF‐1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabeled polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1‐ 14 C]18∶2n−6 and [1‐ 14 C]18∶3n−3), C 18–20 elongase ([U‐ 14 C]18∶4n−3), Δ5 desaturase ([1‐ 14 C]20∶3n−6 and [1‐ 14 C]20∶5n−3), and C 20–22 elongase ([1‐ 14 C]20∶4n−6 and [1‐ 14 C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF‐1 cells was highly active and that C 18–20 elongase and C 20–22 elongase activities were substantial. A deficiency in the desaturation/elongation pathway was clearly identified at the level of the fatty acyl Δ5 desaturase, which was very low, particularly with 20∶4n−3 as substrate. In comparison, the apparent activities of Δ6 desaturase, C 18–20 elongase, and C 20–22 elongase were approximately 94‐, 27‐, and 16‐fold greater than that for Δ5 desaturase toward their respective n−3 polyunsaturated fatty acid substrates. The evidence obtained in the SAF‐1 cell line is consistent with the dietary requirement for C 20 and C 22 highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase activity.