Fatty acid biosynthesis, initial steps (Saccharomyces cerevisiae)

Jump to: navigation, search

Fatty acids are essential to all organisms except for archaea; they are major constituents of cellular membranes, and are used for energy storage and for posttranslational protein modifications. Most organisms are capable of synthesizing long chain (C12:0-C16:0) saturated fatty acids de novo. Although the initiation and termination reactions may vary, the cyclic series of chain-lengthening reactions are essentially the same across all organisms. The fatty acid chain, which starts as a 2-carbon chain from acetyl-CoA, is extended two carbons at a time by the addition of an acetyl group from malonyl-CoA. When the final length of the fatty acid is achieved, fatty acid synthesis is terminated. Each cycle of chain elongation involves 5 reactions with the following enzymatic activities: malonyl transferase, ketoacyl synthase, ketoacyl reductase, 3-hydroxyacyl dehydratase, and enoyl-acyl reductase (EC: 1.3.1.10). In yeast, fatty acid biosynthesis is terminated with the release of fatty acyl-CoAs from fatty acid synthase (FAS), the enzyme complex that carries out de novo fatty acid biosynthesis. Palmitoyl- (C16) and stearoyl-CoA (C18) are the main products in yeast, while myristoyl-CoA (C14) is only produced in small amounts. To synthesize palmitoyl-CoA (C16) one acetyl-CoA and 7 malonyl-CoA molecules are required. The elongation substrate, malonyl-CoA is synthesized from the carboxylation of acetyl-CoA by the biotin-containing enzyme, acetyl-CoA carboxylase). Acetyl-CoA carboxylase is activated by the biotin:apoprotein ligase. Description from YeastPathways https://pathway.yeastgenome.org/