Propionyl-CoA

Definition

Propionyl-CoA is a key metabolic intermediate that is produced during the catabolism of certain amino acids and the breakdown of odd-chain fatty acids. It plays a crucial role in the context of 29.3 Catabolism of Triacylglycerols: β-Oxidation, as it is an important product of this process.

5 Must Know Facts For Your Next Test

1. Propionyl-CoA is produced when odd-chain fatty acids undergo β-oxidation, as the final round of this process yields propionyl-CoA instead of the typical acetyl-CoA.
2. Propionyl-CoA can also be generated during the catabolism of certain amino acids, such as valine, isoleucine, and threonine.
3. Propionyl-CoA must be converted to methylmalonyl-CoA and then to succinyl-CoA in order to enter the citric acid cycle and be fully oxidized for energy production.
4. The conversion of propionyl-CoA to methylmalonyl-CoA is catalyzed by the enzyme propionyl-CoA carboxylase, which requires the cofactor vitamin B12 (cobalamin).
5. Deficiencies in propionyl-CoA carboxylase or vitamin B12 can lead to the accumulation of propionyl-CoA and the development of a condition called propionic acidemia, which can be life-threatening if not properly managed.

Review Questions

• Explain how propionyl-CoA is generated during the catabolism of triacylglycerols through β-oxidation.
  • During the β-oxidation of fatty acids, the final round of this process yields propionyl-CoA instead of the typical acetyl-CoA. This occurs when the fatty acid being broken down has an odd number of carbon atoms. The propionyl-CoA produced must then be converted to methylmalonyl-CoA and subsequently to succinyl-CoA in order to enter the citric acid cycle and be fully oxidized for energy production.
• Describe the role of propionyl-CoA carboxylase and vitamin B12 in the metabolism of propionyl-CoA.
  • The enzyme propionyl-CoA carboxylase catalyzes the conversion of propionyl-CoA to methylmalonyl-CoA, which is then converted to succinyl-CoA and can enter the citric acid cycle. This enzyme requires the cofactor vitamin B12 (cobalamin) to function properly. Deficiencies in either propionyl-CoA carboxylase or vitamin B12 can lead to the accumulation of propionyl-CoA and the development of a condition called propionic acidemia, which can be life-threatening if not properly managed.
• Analyze the importance of propionyl-CoA in the overall context of triacylglycerol catabolism and energy production.
  • Propionyl-CoA is a critical intermediate in the catabolism of triacylglycerols through β-oxidation, particularly when the fatty acids being broken down have an odd number of carbon atoms. The proper metabolism of propionyl-CoA, through its conversion to methylmalonyl-CoA and then succinyl-CoA, allows it to enter the citric acid cycle and be fully oxidized to produce ATP. This highlights the importance of propionyl-CoA in the broader context of energy production from triacylglycerol catabolism. Disruptions in the metabolism of propionyl-CoA can lead to serious metabolic disorders, underscoring its pivotal role in this process.

Related terms

β-Oxidation: The catabolic process by which fatty acids are broken down to generate acetyl-CoA, which can then enter the citric acid cycle to produce ATP.

Odd-Chain Fatty Acids: Fatty acids with an odd number of carbon atoms, which are broken down to produce propionyl-CoA as an intermediate.

Methylmalonyl-CoA: An intermediate formed from propionyl-CoA that is then converted to succinyl-CoA, which can enter the citric acid cycle.