Pathway trait Trait type Mechanism Gene family Example taxa with functional pathway Example taxa without functional pathway
1) 18:0
0/1
De novo fatty acid synthesis Elongation Fatty acid synthase SFA elongases All eukaryotes All eukaryotes
2) 18:0 18:1n-9 (SFA to MUFA)
0/1
∆9 desaturation
First desaturases (Stearoyl-CoA desaturases)
All eukaryotes
3) 18:1n-9 18:2n-6 (MUFA to PUFA)
0/1
∆12 desaturation
Omega desaturases (Methyl-end desaturases)
Plants, protists, fungi, certain invertebrates (Cnidarians, Nematodes, Lophotrochozoans, some Copepods)
Deuterostomes
4) Omega-6 Omega-3
0/1
∆15 desaturation (18:2n-6 18:3n-3)
Omega desaturases (Methyl-end desaturases)
Plants, protists, fungi, certain invertebrates (Cnidarians, Nematodes, Lophotrochozoans, some Copepods)
Deuterostomes
0/1 ∆17 desaturation (C20 n-6 C20 n-3) Omega desaturases (Methyl-end desaturases)
0/1 ∆19 desaturation (C22 n-6 C22 n-3) Omega desaturases (Methyl-end desaturases)
5) ALA EPA and LIN ARA
0/1
∆6 desaturation
Front-end desaturases
Most vertebrates (Fads2 gene), invertebrates
Vascular plants (some can produce 18:4n-3) Most marine teleosts except Elopomorpha (lack Fads1)
0/1 ∆5 desaturation Front-end desaturases Most vertebrates (Fads1 gene); Fish with neofunctionalization of Fads2 (e.g., Zebrafish, Salmon); invertebrates (e.g., nematodes, molluscs, sea urchins)
0/1 ∆8 desaturation Front-end desaturases Mammals, fish (Fads2 gene), invertebrates (e.g., molluscs, sea urchins)
0/1 Elongation (C18 C20) PUFA elongases Most animals
6) EPA DHA and ARA 22:5n-6
0/1
∆4 desaturation
Front-end desaturases
Microalgae, protists, fungi, fish with neofunctionalization of Fads2 (e.g., Rabbit fish)
Vascular plants (no PUFA elongase) Some acanthopterygian fish (lack ∆6 desaturation to C24)
0/1 ∆6 desaturation Front-end desaturases Mammals, fish (Fads2 gene)
0/1 Elongation (C20 C24) PUFA elongases Microalgae, protists, fungi, most animals