Comparsion of Activities of Fatty Acyl Desaturases and Elongases Among Six Teleosts With Different Feeding and Ecological Habits

Abstract

Fatty acyl desaturases 2 (Fads2) and elongases of very-long-chain fatty acid 5 (Elovl5) are two key enzymes involved in the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs), and their activities determine the LC-PUFA biosynthetic ability of teleost. In order to investigate the relation of enzymic activities with fish's feeding habits and ecological habits, the activities of Fads2 and Elovl5 were compared among six teleosts, namely, freshwater carnivorous mandarin fish (Siniperca chuatsi), freshwater herbivorous grass carp (Ctenopharyngodon idellus), marine carnivorous orange-spotted grouper (Epinephelus coioides), marine herbivorous rabbitfish (Siganus canaliculatus), anadromous Atlantic salmon (Salmo salar), and catadromous Japanese eel (Anguilla japonica). Among them, the enzymatic features of Fads2 and Elovl5 from the last five fish species have been characterized, whereas those of S. chuatsi were unknown. And thus, the coding sequences (CDSs) of S. chuatsi fads2 and elovl5 (elovl5a and elovl5b) were isolated, and their functions were further characterized by heterologous expression in yeast. The results showed that S. chuatsi Fads2 has a monofunctional 6 desaturase and that Elovl5a has a higher activity toward C18-C20 PUFAs than has Elovl5b, which showed a noteworthy activity toward C22 PUFAs. The comparison of enzymatic activities among the six teleosts showed that the 6 Fad and Elovl5 activities varied markedly among fish species; in particular, the activity of 6 Fad in C. idellus, S. canaliculatus, and A. japonica was significantly higher than that in S. chuatsi, S. salar, and E. coioides. For C18 PUFA substrates, A. japonica Elovl5 has a higher elongation than has the other tested fish, and it exhibits a higher activity toward the C20 PUFAs. The results suggest that the 6 Fad activity is influenced by both feeding habits and ecological habits, whereas the Elovl5 activity was more affected by the feeding habits. These data enrich our knowledge on LC-PUFA biosynthesis diversity of fatty acid desaturation and elongations in teleosts and provide guidance for the choice of dietary PUFA precursors for farmed fish.

Expression of long-chain polyunsaturated fatty acids biosynthesis genes during the early life-cycle stages of the tropical gar Atractosteus tropicus

“…mykiss salmonids showed that fads2, elovl5 and/or elovl2 are highly expressed in liver, intestine and brain (Morais et al, 2009;Abdul Hamid et al, 2016). The expression patterns and activity of desaturases and elongases are influenced by factors such as phylogeny, and ecological and feeding habits (Garrido et al, 2019;Xie et al, 2020). Therefore, results of transcript abundance in different tissues of A. tropicus are in accordance with previous results in freshwater fish species.…”

Molecular Characterization, Tissue Distribution and Differential Nutritional Regulation of Three n-3 LC-PUFA Biosynthesis-Related Genes in Hybrid Grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

“…However, the gene expression in the kidney was the lowest among all the measured tissue, which was inconsistent with the orange-spotted grouper findings [44]. These results suggest that the diversification of fish LC-PUFA synthesis in different tissues could be associated with factors such as feeding habits, ecological habits, and species-specific evolutionary history [45].…”

Effects of dietary replacement of fish oil with soybean oil on the growth performance, plasma components, fatty acid composition and lipid metabolism of groupers Epinephelus coioides

“…Although high expressions of liver elovl5 and/ or δ6fad genes were observed in fish fed higher SO level diets, the upregulation of genes related to FA desaturation and elongation did not seem to result in increased EPA and DHA tissue contents; instead, it is the dietary SO substitution level that determines the fate of tissue EPA and DHA levels, which indicates that the ability of the grouper to synthesize n-3 LC-PUFAs is very weak. The FA desaturation and elongation activity vary with the fish species (Xie et al, 2020).…”

“…In comparison with warm water fish, marine or carnivorous fish are considered to have limited ability to convert linoleic acid (LA) and linolenic acid (LNA) to n-6 and n-3 LC-PUFAs, such as EPA and DHA, owing to the weak activity of fatty acyl desaturases (FADs) (Castro et al, 2016;Xie et al, 2020). Therefore, further studies on the potential use and role of the dietary SO inclusion in marine fish are required to promote the sustainable development of aquaculture.…”