PathwayStep1865 PathwayStep1864 PathwayStep1863 PathwayStep1862 PathwayStep1861 PathwayStep1860 PathwayStep1858 PathwayStep1857 PathwayStep1859 PathwayStep1854 PathwayStep1853 PathwayStep1856 PathwayStep1855 PathwayStep1852 PathwayStep1851 Activation of alpha-linolenic acid to alpha-linolenoyl-CoA Desaturation of alpha-linoleoyl-CoA to Stearidonoyl-CoA Elongation of stearidonoyl-CoA to eicosatetraenoyl-CoA Desaturation of eicosatetraenoyl-CoA to eicosapentaenoyl-CoA Elongation of eicosapentaenoyl-CoA to docosapentaenoyl-CoA Elongation of docosapentaenoyl-CoA to tetracosapentaenoyl-CoA Formation of DHA-CoA catalysed by 3-ketoacyl-CoA thiolase Conversion of DHA-CoA to docosahexaenoic acid (DHA) Dehydrogenation of 3-hydroxy tetracosahexaenoyl-CoA Formation of DHA-CoA catalysed by sterol carrier protein X (SCPx) Retranslocation of DHA back to ER Hydration of delta2-tetracosaheptaenoyl-CoA to 3-hydroxy tetracosahexaenoyl-CoA Oxidation of tetracosapentaenoyl-CoA to delta2-tetracosaheptaenoyl-CoA Translocation of tetracosahexaenoyl-CoA to peroxisomes Desaturation of tetracosapentaenoyl-CoA to tetracosahexaenoyl-CoA alpha-linolenic acid (ALA) metabolism 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.<br><br>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). Authored: Garapati, P V, 2012-01-11 Edited: Garapati, P V, 2012-01-11 GENE ONTOLOGYGO:0036109 Pubmed16828546 Pubmed8443237 Reactome Database ID Release 432046106 Reactome, http://www.reactome.org ReactomeREACT_121147