Acyl-CoA

Acyl-CoA

Diagram of Acyl-CoA structure

Acyl-CoA is a group of coenzymes involved in the metabolism of fatty acids. They are derivatives of coenzyme A (CoA) and play a crucial role in the beta-oxidation pathway, which is the process of breaking down fatty acids to produce acetyl-CoA, a key molecule in energy production.

Structure

Acyl-CoA consists of a fatty acid chain attached to coenzyme A. The fatty acid chain can vary in length, typically ranging from 2 to 30 carbon atoms. The attachment occurs through a thioester bond between the carboxyl group of the fatty acid and the thiol group of coenzyme A.

Function

Acyl-CoA molecules are essential intermediates in several metabolic pathways:

• Beta-oxidation: Acyl-CoA is the substrate for the beta-oxidation pathway, where it undergoes a series of enzymatic reactions to produce acetyl-CoA, NADH, and FADH2. These products are then used in the citric acid cycle and electron transport chain to generate ATP.

• Lipid biosynthesis: Acyl-CoA is also involved in the synthesis of complex lipids, such as phospholipids and triglycerides.

• Ketogenesis: In the liver, acyl-CoA can be converted into ketone bodies during periods of fasting or low carbohydrate intake.

Beta-Oxidation Process

Illustration of the beta-oxidation process

The beta-oxidation of fatty acids occurs in the mitochondria and involves the following steps:

1. Activation: Fatty acids are activated to form acyl-CoA by the enzyme acyl-CoA synthetase. This reaction requires ATP and occurs in the cytosol.

2. Transport: The acyl-CoA is transported into the mitochondria via the carnitine shuttle.

3. Oxidation: The acyl-CoA undergoes a series of four reactions: dehydrogenation, hydration, another dehydrogenation, and thiolysis. These reactions shorten the fatty acid chain by two carbon atoms, releasing acetyl-CoA.

4. Repetition: The shortened acyl-CoA re-enters the cycle until the entire fatty acid is converted into acetyl-CoA units.

Clinical Significance

Defects in the metabolism of acyl-CoA can lead to metabolic disorders such as medium-chain acyl-CoA dehydrogenase deficiency (MCADD) and other fatty acid oxidation disorders. These conditions can result in hypoglycemia, muscle weakness, and other symptoms due to impaired energy production.

Related Pages

• Coenzyme A
• Fatty acid metabolism
• Beta-oxidation
• Citric acid cycle

Gallery

• 
  Diagram of Acyl-CoA structure
• 
  Illustration of the beta-oxidation process

Acyl-CoA

• 
  Diagram of Acyl-CoA structure
• 
  Illustration of the Beta Oxidation Process