| Definition: |
A fatty acid beta-oxidation pathway by which fatty acids having cis-double bonds on even-numbered carbons are degraded. In this pathway, the intermediate 2,4-dienoyl-CoA is converted to cis-2-enoyl-CoA through one more cycle of the core beta-oxidation pathway. Cis-2-enoyl-CoA cannot be completely degraded via the core beta-oxidation pathway because hydratation of cis-2-enoyl-CoA yields D-3-hydroxyacyl-CoA, which is not a substrate for 3-hydroxylacyl-CoA dehydrogenase. Cis-2-enoyl-CoA must enter the so-called epimerase pathway, which involves converting D-3-hydroxyacyl-CoA to L-3-hydroxyacyl-CoA by 3-hydroxylacyl-CoA epimerase or by two stereo-specific enoyl-CoA hydratases. L-3-hydroxyacyl-CoA then returns to the core beta-oxidation pathway. Fatty acid beta-oxidation begins with the addition of coenzyme A to a fatty acid, and ends when only two or three carbons remain (as acetyl-CoA or propionyl-CoA respectively). |