Crotonyl-CoA

Definition

Crotonyl-CoA is a key intermediate in the beta-oxidation pathway, which is the process of breaking down fatty acids to generate energy for the body. It is formed when the fatty acid is dehydrogenated and the resulting double bond is shifted during the cyclic degradation of the fatty acid chain.

5 Must Know Facts For Your Next Test

1. Crotonyl-CoA is an unsaturated acyl-CoA intermediate that is formed during the beta-oxidation of even-chain fatty acids.
2. The formation of crotonyl-CoA involves the dehydrogenation of the fatty acid chain, which introduces a trans-double bond between the beta and gamma carbon atoms.
3. Crotonyl-CoA is then further metabolized by the enzyme crotonase, which hydrates the double bond to form 3-hydroxybutyryl-CoA.
4. The conversion of crotonyl-CoA to 3-hydroxybutyryl-CoA is a key step in the beta-oxidation pathway, as it prepares the fatty acid chain for the next round of oxidation.
5. Disruptions in the metabolism of crotonyl-CoA can lead to various metabolic disorders, such as medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

Review Questions

• Explain the role of crotonyl-CoA in the beta-oxidation pathway.
  • Crotonyl-CoA is a crucial intermediate in the beta-oxidation pathway, which is the process of breaking down fatty acids to generate energy for the body. During beta-oxidation, the fatty acid chain undergoes a series of dehydrogenation, hydration, and thiolysis reactions. The formation of crotonyl-CoA occurs when the fatty acid is dehydrogenated, resulting in the introduction of a trans-double bond between the beta and gamma carbon atoms. This unsaturated acyl-CoA intermediate is then further metabolized by the enzyme crotonase, which hydrates the double bond to form 3-hydroxybutyryl-CoA, preparing the fatty acid chain for the next round of oxidation.
• Describe the significance of the dehydrogenation reaction that leads to the formation of crotonyl-CoA.
  • The dehydrogenation reaction that forms crotonyl-CoA is a key step in the beta-oxidation pathway because it introduces a double bond into the fatty acid chain. This double bond serves two important purposes: First, it activates the carbon-carbon bond adjacent to the double bond, making it more susceptible to nucleophilic attack during the subsequent hydration reaction catalyzed by crotonase. Second, the presence of the double bond changes the geometry of the fatty acid chain, which is necessary for the proper orientation and positioning of the molecule during the next steps of beta-oxidation. The formation of crotonyl-CoA, therefore, is a critical transition point in the cyclic degradation of fatty acids to generate energy for the body.
• Evaluate the potential consequences of disruptions in the metabolism of crotonyl-CoA.
  • Disruptions in the metabolism of crotonyl-CoA can have serious consequences for an individual's health and well-being. One example is medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, a genetic disorder in which the enzyme responsible for the dehydrogenation of medium-chain fatty acids, including the conversion of octanoyl-CoA to crotonyl-CoA, is deficient or absent. This leads to the accumulation of medium-chain fatty acid intermediates, which can cause hypoglycemia, lethargy, and potentially life-threatening metabolic crises, especially during periods of fasting or illness. Other disruptions in crotonyl-CoA metabolism may also contribute to the development of various metabolic disorders, highlighting the critical importance of this intermediate in the proper functioning of the beta-oxidation pathway and overall energy production within the body.

Related terms

Beta-Oxidation: The process of breaking down fatty acids in the mitochondria to generate acetyl-CoA, which can then enter the citric acid cycle to produce ATP.

Dehydrogenation: The removal of hydrogen atoms from a molecule, often resulting in the formation of a carbon-carbon double bond.

Fatty Acid Degradation: The stepwise breakdown of fatty acid chains to generate acetyl-CoA, which can be used in the citric acid cycle for energy production.