Presentation on Fatty Acid Alpha Beta & Omega Oxidation.: Presentation on Fatty Acid Alpha Beta & Omega Oxidation . Payal Kumari . Reg no: 11006551 Roll No:17 Slide 2: Fatty acids play several important roles: Building blocks for phospholipids and glycolipids Target proteins to membranes High energy source of fuel Fatty acid derivatives are used as hormones and intracellular messengers 2 Introduction Slide 3: TYPES OF FATTY ACID OXIDATION. Alpha fatty acid oxidation : Alpha oxidation (α-oxidation) is a process by which certain fatty acids are broken down by removal of a single carbon from the carboxyl end. In humans, alpha-oxidation is used in peroxisomes to break down dietary phytanic acid, which cannot undergo beta-oxidation due to its β-methyl branch, into pristanic acid. Beta fatty acid oxidation : Beta oxidation is the process by which fatty acids, in the form of Acyl-CoA molecules, are broken down in mitochondria and/or in peroxisomes to generate Acetyl-CoA, the entry molecule for the Citric Acid cycle. 3.Omega fatty acid oxidation: Omega oxidation is a process of fatty acid metabolism in some species of animals. It is an alternative pathway to beta oxidation that, instead of involving the β carbon, involves the oxidation of the omega carbon. The process is normally a minor catabolic pathway for medium-chain fatty acids (10-12 carbon atoms), but becomes more important when β oxidation is defective.In vertebrates, the enzymes for ω oxidation are located in the endoplasmic reticulum of liver and kidney cells,instead of in the mitochondria as with β oxidation. Slide 5: ALPHA OXIDATION Alpha-oxidation of phytanic acid is believed to take place entirely within peroxisomes . Phytanic acid is first attached to CoA to form phytanoyl-CoA . Phytanoyl-CoA is oxidized by phytanoyl-CoA dioxygenase , in a process using Fe 2+ and O 2 , to yield 2-hydroxyphytanoyl-CoA. 2-hydroxyphytanoyl-CoA is cleaved by 2-hydroxyphytanoyl-CoA lyase in a TPP-dependent reaction to form pristanal and formyl-CoA (in turn later broken down into formate and eventually CO 2 ). Pristanal is oxidized by aldehyde dehydrogenase to form pristanic acid(which can then undergo beta-oxidation) . Pathway for Beta-oxidation.: Pathway for Beta-oxidation. Dehydrogenation of fatty acyl-CoA produces a = bond. In second step,water is added to the double bond of the trans enoyl Co-A. The enzyme beta hydroxyacyl CoA dehydrogenase is absolutely specific for the L-stereoisomer of hydroxyacyl-CoA . Last and fourth step is catalysed by acyl-CoA acetyltransferase commonly called thiolase . It promotes a reaction of beta keto-acyl CoA with a molecule of free coenzyme A to split off the carboxyl terminal 2C fragment of the original fatty acid as acetyl- CoA . Beta Oxidation contd…: Beta Oxidation contd … Slide 8: In mitochondria: - only basic enzymes, no modifying enzymes found Acyl-CoA-dehydrogenase Enoyl-CoA-hydratase 3-hydroxyacyl-CoA-dehydrogenase 3-ketoacyl-CoA-thiolase -oxidation of saturated fatty acids (short chain) Slide 9: Acyl-CoA-oxidase Peroxisomal hydratase-dehydrogenase-epimerase (MFP) 3-ketoacyl-CoA-thiolase Enoyl-CoA-hydratase 3-hydroxyacyl-CoA-dehydrogenase -Oxidation of saturated and unsaturated long-chain-fatty acids Enz 1 Enz 2 Enz 3 Enz 4 Substrate + shorter fatty acid chain Slide 10: 10 Each round in fatty acid degradation involves four reactions Fatty acid oxidation. Slide 11: a- and w-oxidation of fatty acids are specialized pathways a-oxidation i.e., removal of one carbon at a time from the carboxyl end of the molecule has been detected in brain tissue. It does not generate CoA intermediates and does not generate high-energy phosphates. w-oxidation is a minor pathway and is brought about by cytochrome P450 in the endoplasmic reticulum. CH3 group is converted to a -CH2OH group that subsequently is oxidized to -COOH, thus forming a dicarboxylic acid. They subsequently undergo ß-oxidation and are excreted in the urine. Omega oxidation: Omega oxidation The enzymes unique to this oxidation are located in the ER of liver and kidney and the preferred substrates are fatty acids of 10 or 12 C atoms. In mammals omega oxidation is normally a minor pathway for fatty acid degradation.