Elementary plant Biochemistry and Biotechnology (2+1)

Biosynthesis of unsaturated fatty acids

• Palmitate and stearate serve as precursors of the two most common monounsaturated fatty acids, palmitoleate, 16:1, (Δ⁹) and oleate, 18:1 (Δ⁹) respectively.
• Each of these fatty acids has a single double bond between C 9 and C 10.
• The double bond is introduced into the fatty acid chain by an oxidative reaction catalysed by fatty acyl CoA desaturase, which is NADPH-dependent enzyme.
• The unsaturated fatty acids, linoleate, 18:2 (Δ⁹,Δ¹²) and * linolenate, 18:3 (Δ^9,12,15) cannot be synthesised by mammals; but plants can synthesise both.
• The desaturases responsible for synthesis of both the above fatty acids are present in endoplasmic reticulum of plants.
• The plant desaturases oxidise phosphatidylcholine-bound oleate and produce polyunsaturated fatty acids and do not directly add double bonds to the fatty acids.
• Once ingested, the linoleate are readily converted to other polyunsaturated fatty acids like Ɣlinolenate, arachidonic acid etc. in animals and human beings.