Fatty acid in mitochondria

FIGURE 25.12 Elongation of fatty acids in mitochondria is initiated by the thiolase reaction. The /3-ketoacyl intermediate thus formed undergoes the same three reactions (in reverse order) that are the basis of /3-oxidation of fatty acids. Reduction of the /3-keto group is followed by dehydration to form a double bond. Reduction of the double bond yields a fatty acyl-CoA that is elongated by two carbons. Note that the reducing coenzyme for the second step is NADH, whereas the reductant for the fourth step is NADPH. 

The carnitine-mediated entry process is the rate-limiting step for oxidation of fatty acids in mitochondria and, as discussed later, is a regulation point. Once inside the mitochondrion, the fatty acyl-CoAis acted upon by a set of enzymes in the matrix. 

Kunau, W.H., Dommes, V, Schulz, H. (1995) /3-Oxidation of fatty acids in mitochondria, peroxisomes, and bacteria a century of continued progress. Prog. Lipid Res. 34, 267-342. 

Fatty Acid Oxidation Yields Large Amounts of ATP Additional Enzymes Are Required for Oxidation of Unsaturated Fatty Acids in Mitochondria Ketone Bodies Formed in the Liver Are Used for Energy in Other Tissues Summary of Fatty Acid Degradation Biosynthesis of Saturated Fatty Acids... 

Additional Enzymes Are Required for Oxidation of Unsaturated Fatty Acids in Mitochondria... 

There are several drugs that inhibit beta oxidation of fatty acids in mitochondria leading to lipid accumulation, such as aspirin, valproic acid, and tetracyclines. 

A FIGURE 8-7 Summary of the aerobic oxidation of pyruvate and fatty acids in mitochondria. The outer membrane is freely permeable to all metabolites, but specific transport proteins (colored ovals) in the inner membrane are required to import pyruvate (yellow), ADP (green), and P (purple) into the matrix and to export ATP (green). NADH generated in the cytosol is not transported directly to the matrix because the inner membrane is impermeable to NAD and NADH instead, a shuttle system (red) transports electrons from cytosolic NADH to NAD in the matrix. O2 diffuses into the matrix and CO2 diffuses out. Stage 1 Fatty acyl groups are transferred from fatty acyl CoA and transported across the inner membrane via a special carrier (blue oval) and then reattached to CoA on the matrix side. 

Oxidation of fatty acids In mitochondria yields acetyl CoA, which enters the citric acid cycle, and the reduced coenzymes NADH and FADH2. Subsequent oxidation of these metabolites Is coupled to formation of ATP. 

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