University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

8

Pages:

5
Author:

Sheha A.

Oxidation in the mitochondrial matrix Steps of β-oxidation of fatty acid undergo following reaction Dehydrogenation: Fatty acyl CoA is dehydrogenated by the enzyme acyl CoA dehydrogenase. The product of this reaction is a trans-2-enoyl CoA. FAD acts as an electron acceptor. Hydration: In this step, water is added to the double bond of trans-2-enoyl CoA to form β-hydroxy acyl CoA in the presence of enoyl CoA hydratase. Dehydrogenation: β-hydroxy acyl CoA is dehydrogenated to form β-keto acyl CoA by the action of β-hydroxy acyl CoA dehydrogenase. NAD+ is the electron acceptor. Thiolysis (Cleavage): The final step of β-oxidation is the liberation of a 2-carbon fragment (acetyl CoA) from fatty acyl CoA. This occurs by a thiolytic cleavage catalyzed by β-keto acyl CoA thiolase. Energy Production of Beta-Oxidation This is explained by taking the example of long chain fatty acid that is palmitate. Palmitate undergoes Beta-Oxidation, it passes through 7 cycles of Beta-Oxidation and oxidise 1 molecule of Palmitoyl CoA to 8 molecules of Acetyl CoA. The overall reaction can be written as, Palmitoyl CoA + 7 CoA + 7 FAD + 7 NAD+ + 7 H2O -> 8 Acetyl CoA + 7 FADH2 + 7 NADH + H+ Each molecule of FADH2 and NADH produced 2 & 3 ATP respectively. Thus total 35 ATP is produced in 7 rounds of Beta-Oxidation. In addition to this, Acetyl CoA produced by Beta-Oxidation enters the citric acid cycle, giving 12 ATP for each molecule of Acetyl CoA. Therefore 96 ATP are produced from 8 molecules of Acetyl CoA produced. Thus total 131 ATP are produced. During activation, 2 ATP are used in the activation of fatty acids. Therefore, net gain per molecule of palmitate is 129 ATP. End Product of Beta-Oxidation Beta-Oxidation of even chain fatty acids gives only Acetyl CoA. Beta-Oxidation of odd chain fatty acids gives both Acetyl CoA and Propionyl CoA. Propionyl CoA is converted to succinyl CoA, which is the metaboliate of TCA cycle. Function of Beta-Oxidation Provision of energy in condition of limited carbohydrate availability. Ketone body formation (from acetyl CoA). Regulation of Beta-Oxidation Beta-oxidation is regulated by availability of fatty acid, which in turn depends on the lipolysis of adipose tissue by hormone sensitive lipase. Hormone sensitive lipase is stimulated by glucagon.