Diversification of substrate specificities in teleostei Fads2: characterization of Δ4 and Δ6Δ5 desaturases of Chirostoma estor

Abstract

Biosynthesis of long-chain PUFAs (LC-PUFAs) in vertebrates involves sequential desaturation and elongation of C 18 PUFA, linoleic acid (LOA; 18:2n-6), and ␣ -linolenic acid (LNA; 18:3n-3) ( 1 ). Synthesis of arachidonic acid (ARA; 20:4n-6) and EPA (20:5n-3) from LOA and LNA, respectively, utilizes the same enzymes and pathways. The pre dominant pathway involves ⌬ 6 desaturation of LOA or LNA to 18:3n-6/18:4n-3 that are elongated to 20:3n-6/20:4n-3 followed by ⌬ 5 desaturation to ARA/EPA ( 1 ), but an alternative pathway with initial elongation of LOA or LNA followed by ⌬ 8 desaturation, an inherent ability of some ⌬ 6 desaturases, may be possible ( 2 ). Biosynthesis of DHA (22:6n-3) from EPA can also occur by two pathways. First, the so-called "Sprecher pathway" involves two sequential elongation steps from EPA to 24:5n-3 and a subsequent ⌬ 6 desaturation to 24:6n-3, followed by peroxisomal chain shortening ( 3 ). Second, a more direct pathway has been postulated in some marine fi sh that involves elongation of EPA to docosapentaenoic acid (22:5n-3) followed by ⌬ 4 desaturation to DHA ( 4,5 ).Dietary PUFAs are essential in fi sh, although requirements vary with species ( 6, 7 ). Generally, C 18 PUFAs can satisfy essential FA requirements of freshwater and salmonid species, but most marine fi sh have a requirement for LC-PUFAs such as EPA and DHA ( 8 ). Differing essential FA requirements have been linked to differences in the complement of fatty acyl desaturase (Fads) and elongase of very longchain FA (Elovl) genes ( 9-31 ). Thus, the dependence of Abstract Currently existing data show that the capability for long-chain PUFA (LC-PUFA) biosynthesis in teleost fi sh is more diverse than in other vertebrates. Such diversity has been primarily linked to the subfunctionalization that teleostei fatty acyl desaturase (Fads)2 desaturases have undergone during evolution. We previously showed that Chirostoma estor , one of the few representatives of freshwater atherinopsids, had the ability for LC-PUFA biosynthesis from C 18 PUFA precursors, in agreement with this species having unusually high contents of DHA. The particular ancestry and pattern of LC-PUFA biosynthesis activity of C. estor make this species an excellent model for study to gain further insight into LC-PUFA biosynthetic abilities among teleosts. The present study aimed to characterize cDNA sequences encoding fatty acyl elongases and desaturases, key genes involved in the LC-PUFA biosynthesis. Results show that C. estor expresses an elongase of very long-chain FA (Elovl)5 elongase and two Fads2 desaturases displaying ⌬ 4 and ⌬ 6/ ⌬ 5 specifi cities, thus allowing us to conclude that these three genes cover all the enzymatic abilities required for LC-PUFA biosynthesis from C 18 PUFA. In addition, the specifi cities of the C. estor Fads2 enabled us to propose potential evolutionary patterns and mechanisms for subfunctionalization of Fads2 among fi sh lineages. -GA-2010-276916, LONGFA). Additional funding was obtained from CONACYT, Mexico (INSAM FOINS 102/201...

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

“…While this is a common trait among Elovl4b-like enzymes [6, 8, 11, 29, 33], the ability of the C. gariepinus Elovl4a to produce VLC-PUFA up to 36 carbons was somewhat unexpected since the only Elovl4a characterized so far from D. rerio showed little ability to biosynthesize VLC-PUFA [6]. Whereas current evidence does not allow us to clarify which of the two Elovl4a phenotypes ( D. rerio or C. gariepinus ) is more prevalent among teleosts, the apparent differences might be in response to ecological and evolutionary factors as previously hypothesized for both elongases [5, 21] and desaturases [35, 36]. Irrespective of the mechanism driving the distinct phenotype among Elovl4a enzymes, it is clear that the C. gariepinus orthologue was very efficient in the production of VLC-PUFA from exogenously supplemented PUFA substrates.…”

Biosynthesis of Polyunsaturated Fatty Acids in Sea Urchins: Molecular and Functional Characterisation of Three Fatty Acyl Desaturases from Paracentrotus lividus (Lamark 1816)

“…When additional PUFA substrates were exogenously supplied, these remained unmodified by control yeast confirming that the S . cerevisiae yeast strain INv Sc 1 lack Δ4, Δ5, Δ6 and Δ8 desaturase activities [42]. …”

Insights into the phylogenetic and molecular evolutionary histories of Fad and Elovl gene families in Actiniaria

“…Research investigating the Fad and Elovl gene families that desaturate and elongate LC‐PUFAs has largely been restricted to bilaterian taxa (Carmona‐Antoñanzas et al., 2011; Castro et al., 2012; Fonseca‐Madrigal et al., 2014; Kabeya et al., 2017; Li et al., 2017; Li et al., 2010; Mohd‐Yusof et al., 2010; Monroig, Guinot, et al., 2012; Monroig, Navarro, et al., 2012; Monroig, Webb, et al., 2011; Monroig et al., 2010, 2016, 2017, 2013; Morais et al., 2009; Surm et al., 2015). We have investigated the phylogenetic and molecular evolutionary histories of the Fad and Elovl gene families in phylum Cnidaria, to provide insights into evolution and the distribution of these gene families in Metazoa outside of bilaterian taxa.…”