fatty acid beta-oxidation

Definition

Target type: biologicalprocess

A fatty acid oxidation process that results in the complete oxidation of a long-chain fatty acid. Fatty acid beta-oxidation begins with the addition of coenzyme A to a fatty acid, and occurs by successive cycles of reactions during each of which the fatty acid is shortened by a two-carbon fragment removed as acetyl coenzyme A; the cycle continues until only two or three carbons remain (as acetyl-CoA or propionyl-CoA respectively). [GOC:mah, ISBN:0198506732, MetaCyc:FAO-PWY]

Fatty acid beta-oxidation is a central metabolic pathway responsible for breaking down fatty acids into acetyl-CoA, a molecule that can be used for energy production in the citric acid cycle. This process occurs primarily in the mitochondria of eukaryotic cells.

The process of beta-oxidation can be divided into four main steps:

1. **Activation and Transport:**
- Fatty acids are activated by attaching them to coenzyme A (CoA) to form fatty acyl-CoA. This reaction requires energy from ATP.
- Activated fatty acyl-CoA is then transported into the mitochondrial matrix via the carnitine shuttle.

2. **Oxidation:**
- The fatty acyl-CoA undergoes a series of four enzymatic reactions:
- Dehydrogenation by acyl-CoA dehydrogenase, producing a trans double bond between carbons 2 and 3.
- Hydration by enoyl-CoA hydratase, adding water across the double bond to form a hydroxyl group.
- Oxidation by 3-hydroxyacyl-CoA dehydrogenase, oxidizing the hydroxyl group to a ketone.
- Thiolysis by thiolase, cleaving the molecule between the alpha and beta carbons, releasing acetyl-CoA and a shorter fatty acyl-CoA.

3. **Repeat Cycle:**
- The shorter fatty acyl-CoA enters the cycle again, repeating steps 2 and 3 until the fatty acid is completely broken down into acetyl-CoA molecules.

4. **Energy Production:**
- The acetyl-CoA generated by beta-oxidation enters the citric acid cycle, where it is further oxidized to produce ATP.
- The reducing equivalents (NADH and FADH2) generated during beta-oxidation also contribute to ATP production through oxidative phosphorylation.

Beta-oxidation is a vital process for energy metabolism, particularly during periods of fasting or prolonged exercise. It allows the body to utilize stored fat as a fuel source. Additionally, beta-oxidation plays a role in other metabolic processes, such as the synthesis of certain amino acids and cholesterol.'
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Proteins (9)

Compounds (267)