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 |
|