Lipid Metabolism II PDF

Essential Biochemistry 5th Edition Charlotte W. Pratt | Kathleen Cornely Lipid Metabolism II Chapter 17  Objectives Describe the steps in fatty acid degradation Even-numbered carbon fatty acids Odd-number carbon fatty acids Un...

Essential Biochemistry 5th Edition Charlotte W. Pratt | Kathleen Cornely Lipid Metabolism II Chapter 17  Objectives Describe the steps in fatty acid degradation Even-numbered carbon fatty acids Odd-number carbon fatty acids Unsaturated fatty acids  Fatty acid degradation aka -oxidation of fatty acids © 2014 John Wiley & Sons, Inc. All rights reserved. Triacylglycerols are the primary source of fatty acids. © 2014 John Wiley & Sons, Inc. All rights reserved. Fatty acids are activated before they are degraded. Activated fatty acids are acylated to CoA. Reaction is driven by ATP hydrolysis. 2 ATP equivalents are used Fatty acylCoA synthetase © 2014 John Wiley & Sons, Inc. All rights reserved.  β Oxidation occurs in the mitochondrial matrix Acyl groups are transferred via carnitine. © 2014 John Wiley & Sons, Inc. All rights reserved. Each round of β oxidation has four reactions. Acyl-CoA is degraded into acetyl-CoA. Let’s look at the reactions of b oxidation more© 2014 John Wiley & Sons, Inc. All rights closely. reserved. β Oxidation   © 2014 John Wiley & Sons, Inc. All rights reserved. β Oxidation © 2014 John Wiley & Sons, Inc. All rights reserved. β Oxidation © 2014 John Wiley & Sons, Inc. All rights reserved. β Oxidation © 2014 John Wiley & Sons, Inc. All rights reserved. β Oxidation results in ATP production. © 2014 John Wiley & Sons, Inc. All rights reserved. Oxidation of odd-chain fatty acids yields propionyl-CoA. O H3C CH2 C SCoA Propionyl CoA ATP + CO2 Methylmalonyl mutase requires ADP + Pi cobalamine O - OOC CH C SCoA CH3 Methylmalonyl CoA Methylmalonyl mutase O O O - OOC H2C CH2 C SCoA H3C C COO- H3C C SCoA Succinyl CoA Pyruvate Acetyl CoA TCA Cycle TCA Cycle (anaplerotic) © 2014 John Wiley & Sons, Inc. All (substrate) rights reserved. Unsaturate d fatty acids yield less energy than saturated fatty acids. NADPH is used -2.5 ATP QH2 is by-passed -1.5 ATP © 2014 John Wiley & Sons, Inc. All rights reserved. Some fatty acid oxidation occurs in peroxisomes Very long chain fatty acids Chain shortening Electrons are transferred to molecular oxygen directly instead of ubiquinone (first step) H2O2 is produced which is broken down by catalase. Branched fatty acids © 2014 John Wiley & Sons, Inc. All rights reserved. Summary Fatty acid degradation TAG hydrolysis, Activation of fatty acids Carnitine transporter Beta oxidation--steps Even-carbon FA: Total energy produced Odd-carbon FA, unsaturated FA Peroxisomes Long-chain FA, branched-chain FA © 2014 John Wiley & Sons, Inc. All rights reserved.