Lipids

, Volume 34, Issue 5, pp 433–440

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

Article

DOI: 10.1007/s11745-999-0382-8

Cite this article as:
Tocher, D.R. & Ghioni, C. Lipids (1999) 34: 433. doi:10.1007/s11745-999-0382-8

Abstract

Marine fish have an absolute dietary requirement for C20 and C22 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 C18–20 elongase activity. Recent research in turbot cells found low C18–20 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 ([1-14C]18∶2n−6 and [1-14C]18∶3n−3), C18–20 elongase ([U-14C]18∶4n−3), Δ5 desaturase ([1-14C]20∶3n−6 and [1-14C]20∶5n−3), and C20–22 elongase ([1-14C]20∶4n−6 and [1-14C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and that C18–20 elongase and C20–22 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, C18–20 elongase, and C20–22 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 C20 and C22 highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase activity.

Abbreviations

AS

Atlantic salmon cells

BHT

butylated hydroxytoluene

BSA

bovine serum albumin

EFA

essential fatty acid

FAF-BSA

fatty acid free-BSA

FAME

fatty acid methyl ester

FBS

fetal bovine serum

HBSS

Hank's balanced salt solution (without Ca2+ and Mg2+)

HPTLC

high-performance thin-layer chromatography

HUFA

highly unsaturated fatty acids (≥C20 with ≥3 double bonds)

PC

phosphatidylcholine

PE

phosphatidylethanolamine

PUFA

polyunsaturated fatty acid

RTG-2

rainbow trout cells

SAF-1

seam bream cell line, developed from fin tissue without immortalization

TF

turbot fin cells

TLC

thin-layer chromatography

Copyright information

© AOCS Press 1999

Authors and Affiliations

  1. 1.Unit of Aquatic Biochemistry, Institute of AquacultureUniversity of StirlingStirlingScotland

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