Category: biosynthesis
Mammals lack the desaturases to make omega-3 (ω3) and omega-6 (ω6) fatty acids de novo — they must come from diet. ALA (α-linolenic, ω3) → EPA → DHA via FADS2 (Δ6-desaturase) + elongases + FADS1 (Δ5). Conversion rate ALA → EPA → DHA is low (<10%) — explains why dietary EPA/DHA from fish oil has effects ALA supplementation doesn't reproduce. Linoleic (ω6) → arachidonic acid (AA) via the same enzyme set — competes with ω3 desaturation. SPMs (specialized pro-resolving mediators): from EPA → E-series resolvins; from DHA → D-series resolvins + protectins + maresins. SPMs actively terminate inflammation (vs glucocorticoids which suppress it) — therapeutic interest is growing.