Alpha-linolenic acid (ALA, 18:3(n-3)) is an omega-3 fatty acid, supplied through diet as it cannot be synthesized by humans. ALA has an important role in human health. It is converted to long chain more unsaturated n-3 fatty acids by a series of alternating desaturation and elongation reactions. Omega-3 products of ALA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reduce inflammation and may help lower risk of chronic diseases, such as heart disease and arthritis. All the desaturation and elongation steps occur in the endoplasmic reticulum (ER) except for the final step which requires translocation to peroxisomes for partial beta-oxidation.
The alpha-linolenic acid pathway involves the following steps: 18:3(n-3)--> 18:4(n-3)-->20:4(n-3)-->20:5(n-3)-->22:5(n-3)-->24:5(n-3)-->24:6(n-3)-->22:6(n-3). Two desaturation enzymes are involved in this process: delta-6 desaturase that converts 18:3(n-3) to 18:4(n-3) and 24:5(n-3) to 24:6(n-3) respectively, delta-5 desaturase 20:4(n-3) to 20:5(n-3). (Sprecher 2002).