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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.

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Parchment, a biologically based material obtained from the processed hides of animals such as cattle and sheep, has been used for millennia as a writing medium. Although numerous studies have concentrated on the structure and degradation of collagen within parchment, little attention has been paid to noncollagenous components, such as lipids. In this study, we present the results of biochemical and structural analyses of historical and newly manufactured parchment to examine the potential role that lipid plays in parchment stability. The lipid fraction extracted from the parchments displayed different fatty acid compositions between historical and reference materials. Gas chromatography, small-angle X-ray scattering, and solid-state NMR were used to identify and investigate the lipid fraction from parchment samples and to study its contribution to collagen structure and degradation. We hypothesize that the origin of this lipid fraction is either intrinsic, attributable to incomplete fat removal in the manufacturing process, or extrinsic, attributable to microbiological attack on the proteinaceous component of parchments. Furthermore, we consider that the possible formation of protein-lipid complexes in parchment over the course of oxidative degradation may be mediated by reactive oxygen species formed by lipid peroxidation. Parchment is a material of biological origin that has been used for centuries as a foundation for historical documents and works of art, including most of the written history of Europe. Consequently, the conservation of parchment has frequently been a foremost concern. Many early methods of intervention did more harm than good to the original documents, and the work of modern conservators is often made more difficult because they have to not only preserve the historical material but also undo earlier treatments or cope with the damage caused by overzealous washing, flattening, or other methods applied in the past (1).Some recent work has focused on the protein structure of parchment and changes to the material on the molecular level over time. Parchment, primarily originating from the hides of cattle, sheep, and goats, is predominantly composed of type I collagen, along with some associated macromolecules such as proteoglycans (2). The hierarchical structure of collagen in a feltwork, which provided mechanical strength to the skin of the animal when it was alive, is now responsible for maintaining the parchment as a viable storage medium. As the collagen degrades over time, the parchment loses strength, becomes brittle, and deteriorates to the point that it can no longer be used. The basis for the biodegradation of collagen within parchment is largely unresolved and is the focus of several current and past research programs, which intend to minimize the loss of cultural and historical artifacts resulting from the biodegradation of collagen in parchment (3)(4)(5).The presence of a lipid fraction in parchment has not been examined extensively, nor has the role that lipids may play in t...

The TF cell line, derived from a carnivorous marine teleost, the turbot (Scophthalmus maximus), is known to have a reduced rate of polyunsaturated fatty acid (PUFA) biosynthesis.In order to establish the enzymic step responsible, the metabolic conversions of a range of PUFA including the key intermediates of n-3PUFA metabolism, stearidonic acid (18:4n-3) and its elongation product 20:4n-3, were studied in TF cells and compared with the AS cell line derived from Atlantic salmon (Salmo salar). Cells were cultured in the presence of unlabelled (25 µM 3