Fads2b Plays a Dominant Role in ∆6/∆5 Desaturation Activities Compared with Fads2a in Common Carp (Cyprinus carpio)

Abstract

Highly unsaturated fatty acids (HUFAs) are essential for mammalian health, development and growth. However, most mammals, including humans, are incapable of synthesizing n-6 and n-3 HUFAs. Fish can convert C18 unsaturated fatty acids into n-6 and n-3 HUFAs via fatty acid desaturase (Fads), in which Fads2 is a key enzyme in HUFA biosynthesis. The allo-tetraploid common carp theoretically encode two duplicated fads2 genes. The expression patterns and desaturase functions of these two homologous genes are still unknown. In this study, the full length of the fads2a and fads2b were identified in common carp (Cyprinus carpio). Expression analyses indicate that both genes were mainly expressed in the liver and the expression of fads2b is higher than fads2a at different developmental stages in carp embryos. Heterogenous expression and 3D docking analyses suggested that Fads2b demonstrated stronger ∆6 and ∆5 desaturase activities than Fads2a. The core promotor regions of fads2a and fads2b were characterized and found to have different potential transcriptional binding sites. These results revealed the same desaturase functions, but different activities of two homologues of fasd2 genes in common carp. The data showed that fads2b played a more important role in HUFA synthesis through both expression and functional analyses.

Characterization and Functional Analysis of Fads Reveals Δ5 Desaturation Activity during Long-Chain Polyunsaturated Fatty Acid Biosynthesis in Dwarf Surf Clam Mulinia lateralis

“…This result suggests that MulFadsB transcripts in the eggs and early larvae are maternally derived rather than endogenously expressed [42]. A similar maternal expression pattern of Fads has also been reported in Danio rerio [42], Common Carp Cyprinus carpio [38], and noble scallop C. nobilis [40]. While the MulFadsA transcript was low at the early developmental stage, it increased dramatically from blastula stages to juvenile stages, indicating that ∆5 Fads may be a critical enzyme in the biosynthesis of PUFAs that are needed in normal development during the early stages in mollusks [40] and other animals [42].…”

“…Typical front-end desaturases of animals in the biosynthesis of LC-PUFAs include Δ4, Δ5, Δ6, and Δ8 fatty acid desaturases. Various Fads genes demonstrating a range of desaturation activity, such as Δ4, Δ5, Δ6, Δ8, Δ5/6, and Δ6/8, have been identified in mammals and teleost fish [ 30 , 34 , 35 , 36 , 37 , 38 ]. In addition, a series of studies have demonstrated that Fads with ∆5, Δ6, or Δ8 activity appear to be widely distributed among mollusks, including cephalopods [ 12 , 39 ], gastropods [ 13 ], and bivalves [ 14 , 15 , 19 , 40 ].…”

Contribution of elovl5a to Docosahexaenoic Acid (DHA) Synthesis at the Transcriptional Regulation Level in Common Carp, Cyprinus carpio

“…The biosynthesis of PUFAs in fish is a process in which LA and ALA are used as substrates to synthesize PUFA through continuous desaturation and elongation reactions. This synthesis pathway is mainly catalyzed by fatty acid desaturase (Fads) that catalyzes the desaturation reaction and elongase of very-long-chain fatty acids (Elovl) that catalyze the carbon chain extension reaction [7,8]. The elovl gene family, which encodes the synthesis of C18 or longer chain fatty acids [9], is a rate-limiting enzyme in these reaction steps [10], playing a crucial role in fatty acid synthesis [11].…”