Elongation of very Long‐Chain (>C₂₄) Fatty Acids in Clarias gariepinus: Cloning, Functional Characterization and Tissue Expression of elovl4 Elongases

Abstract

Elongation of very long-chain fatty acid 4 (Elovl4) proteins participate in the biosynthesis of very long-chain (>C24) saturated and polyunsaturated fatty acids (FA). Previous studies have shown that fish possess two different forms of Elovl4, termed Elovl4a and Elovl4b. The present study aimed to characterize both molecularly and functionally two elovl4 cDNA from the African catfish Clarias gariepinus. The results confirmed that C. gariepinus possessed two elovl4-like elongases with high homology to two previously characterized Elovl4 from Danio rerio, and thus they were termed accordingly as Elovl4a and Elovl4b. The C. gariepinus Elovl4a and Elovl4b have open reading frames (ORF) of 945 and 915 base pairs, respectively, encoding putative proteins of 314 and 304 amino acids, respectively. Functional characterization in yeast showed both Elovl4 enzymes have activity towards all the PUFA substrates assayed (18:4n-3, 18:3n-6, 20:5n-3, 20:4n-6, 22:5n-3, 22:4n-6 and 22:6n-3), producing elongated products of up to C36. Moreover, the C. gariepinus Elovl4a and Elovl4b were able to elongate very long-chain saturated FA (VLC-SFA) as denoted by increased levels of 28:0 and longer FA in yeast transformed with elovl4 ORF compared to control yeast. These results confirmed that C. gariepinus Elovl4 play important roles in the biosynthesis of very long-chain FA. Tissue distribution analysis of elovl4 mRNAs showed both genes were widely expressed in all tissues analyzed, with high expression of elovl4a in pituitary and brain, whereas female gonad and pituitary had the highest expression levels for elovl4b.

Essential fatty acid metabolism and requirements of the cleaner fish, ballan wrasse Labrus bergylta : Defining pathways of long-chain polyunsaturated fatty acid biosynthesis

“…As we have demonstrated here that ballan wrasse Elovl5 is not able to elongate 22:5n-3 to 24:5n-3, and the genome assembly available for ballan wrasse confirmed the lack of an elovl2, another mechanism would be required for the provision of the 24:5n-3 required for the Sprecher pathway. This will likely be via elongation of 22:5n-3 by Elovl4, enzymes that can be identified in ballan wrasse genomic and transcriptomic databases (data not shown), and that have been demonstrated to be capable of elongating 22:5n-3 in all fish species investigated (Monroig et al, 2010;Jin et al, 2017;Oboh et al, 2017b). Since the ballan wrasse Fads2 characterised herein did not show Δ4 desaturase capability, it can be deduced that DHA biosynthesis in ballan wrasse can only occur through the Sprecher pathway.…”

“…Importantly, the elovl2 gene has been lost during the evolution of teleosts and, as a consequence, the vast majority of marine fish species currently farmed do not possess this type of elongase (Castro et al, 2016). It has been postulated that loss of elongation capacity towards C 22 PUFA through the absence of Elovl2 in marine fish can be partly compensated by another elongase, Elovl4 (Monroig et al, 2010;2011) since, in addition to the biosynthesis of very long-chain (> C 24 ) PUFA (Oboh et al, 2017b), fish Elovl4 can elongate C 22 PUFA (Monroig et al, 2010;Jin et al, 2017). The above mentioned diversity of gene complement and substrate specificities in fish LC-PUFA biosynthesising enzymes demonstrates that species-specific studies on Fads and Elovl are required to unequivocally elucidate the capacity to utilise dietary VO of new fish species that are candidates for aquaculture diversification.…”

A chromosome-level assembly of the black tiger shrimp (Penaeus monodon) genome facilitates the identification of novel growth-associated genes

“…The results agree with the previous studies reported that additional of high HUFA such as linoleic (LOA, 18:2n–6), linolenic (LNA, 18:3n–3), eicosapentaenoic acid (EPA, 20:5n–3) or docosahexaenoic acid (DHA, 22:6n–3) in diet could promote the growth (Glencross, Smith, Thomas, & Williams, 2002a, 2002b). Interestingly, elovl4 that synthesizes very long-chain (>C24) saturated and polyunsaturated fatty acids (Oboh, Navarro, Tocher, & Monroig, 2017) was expressed at a higher level in the slow-growing shrimp than in the fast-growing one. In gilthead sea bream Sparus aurata , high amount of LNA and long-chain fatty acid adversely affected growth (Turkmen et al, 2019).…”

Complete repertoire of long‐chain polyunsaturated fatty acids biosynthesis enzymes in a cyprinid, silver barb ( Barbonymus gonionotus ): Cloning, functional characterization and dietary regulation of Elovl2 and Elovl4

“…While majority of the studies on aquaculture candidate species focused on Elovl5 and Elovl2, studies on Elovl4 in a wide number of species have recently began to emerge (Betancor et al, 2020; Carmona‐Antonanzas et al., 2011; Jin, Monroig, Navarro, Tocher, & Zhou, 2017; Kabeya et al., 2015; Li, Monroig, Navarro, et al, 2017; Li, Monroig, Navarro, et al, 2017; Monroig et al., 2012; Monroig, Webb, et al, 2011; Oboh, Navarro‐Guillén, Tocher, & Monroig, 2017; Zhao et al, 2019). Collective, these results indicate that while both the mammalian and teleost Elovl4 play a role in the elongation of very long‐chain fatty acids (VLC‐FA) such as > C24 SFA and PUFA, the teleost Elovl4 could also catalyse the elongation of C22 PUFA substrates to C24 products, (Agbaga et al., 2008; Castro, Tocher, & Monroig, 2016; Monroig, Zheng, et al, 2010).…”