- Oxidation of Saturated Fatty Acids

Inside of the mitochondrion, fatty acyl-CoAs are oxidized in a series of steps that each release a two-carbon fragment, in the form of acetyl-CoA. Each step involves four reactions-dehydrogenation, hydration, dehydrogenation, and thiolytic cleavage (Figure 18.16). The individual reactions are summarized as follows:

1. Fatty acyl-CoA + E-FAD <=> Trans-2-Enoyl-CoA + E-FADH2 (catalyzed by Fatty Acyl-CoA Dehydrogenase)(Figure 18.16). The FAD and FADH2 in the reaction are enzyme-bound. Electrons from FADH2 are donated to coenzyme Q in the electron transport system (Figure 18.17).

2. Trans-2-Enoyl-CoA + H2O <=> L-3-Hydroxyacyl-CoA (catalyzed by Enoyl-CoA Hydratase)(Figure 18.16).

3. L-3-Hydroxyacyl-CoA + NAD⁺ <=> 3-Ketoacyl-CoA + NADH + H⁺  (catalyzed by 3-Hydroxyacyl-CoA Dehydrogenase)(Figure 18.16).

4. 3-Ketoacyl-S-CoA + CoASH <=> Acyl-CoA + Acetyl-CoA (catalyzed by -Ketothiolase)(Figure 18.16).

A modified form of -oxidation of saturated fatty acids occurs in peroxisomes, organelles that are present in most eukaryotic cells.

Peroxisomal -Oxidation