Even-numbered Saturated Fatty Acids
Once inside the mitochondria, each cycle of β-oxidation, liberating a two carbon unit (acetyl-CoA), occurs in a sequence of four reactions:
| Description | Diagram | Enzyme | End product |
| Dehydrogenation by FAD: The first step is the oxidation of the fatty acid by Acyl-CoA-Dehydrogenase. The enzyme catalyzes the formation of a double bond between the C-2 and C-3. | acyl CoA dehydrogenase | trans-Δ2-enoyl-CoA | |
| Hydration: The next step is the hydration of the bond between C-2 and C-3. The reaction is stereospecific, forming only the L isomer. | enoyl CoA hydratase | L-β-hydroxyacyl CoA | |
| Oxidation by NAD+: The third step is the oxidation of L-β-hydroxyacyl CoA by NAD+. This converts the hydroxyl group into a keto group. | L-β-hydroxyacyl CoA dehydrogenase | β-ketoacyl CoA | |
| Thiolysis: The final step is the cleavage of β-ketoacyl CoA by the thiol group of another molecule of CoA. The thiol is inserted between C-2 and C-3. | β-ketothiolase | An acetyl-CoA molecule, and an acyl-CoA molecule that is two carbons shorter |
This process continues until the entire chain is cleaved into acetyl CoA units. The final cycle produces two separate acetyl CoAs, instead of one acyl CoA and one acetyl CoA. For every cycle, the Acyl CoA unit is shortened by two carbon atoms. Concomitantly, one molecule of FADH2, NADH and acetyl CoA are formed.
Read more about this topic: Beta Oxidation
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