Propionyl-CoA

Definition

Propionyl-CoA is a three-carbon molecule formed from the metabolism of certain amino acids and fatty acids, specifically those with odd-numbered carbon chains. It serves as an important intermediate in metabolic pathways, linking the degradation of these compounds to the citric acid cycle through its conversion to succinyl-CoA, thereby connecting lipid, carbohydrate, and protein metabolism.

5 Must Know Facts For Your Next Test

1. Propionyl-CoA is generated from the breakdown of certain amino acids like valine, isoleucine, and threonine, as well as from the metabolism of odd-chain fatty acids.
2. The conversion of propionyl-CoA to succinyl-CoA involves a vitamin B12-dependent enzyme, highlighting the importance of this vitamin in energy metabolism.
3. Propionyl-CoA can also enter gluconeogenesis, allowing for the synthesis of glucose from non-carbohydrate sources.
4. The metabolism of propionyl-CoA is particularly important in ruminants and other animals that rely on fermentation for energy production from plant materials.
5. Disruptions in propionyl-CoA metabolism can lead to metabolic disorders, including propionic acidemia, which is characterized by an accumulation of propionic acid in the body.

Review Questions

• How does propionyl-CoA connect lipid and protein metabolism?
  • Propionyl-CoA serves as a crucial link between lipid and protein metabolism by acting as an intermediate formed during the breakdown of odd-chain fatty acids and certain amino acids. When odd-chain fatty acids are metabolized, they produce propionyl-CoA. Similarly, specific amino acids contribute to its formation. This connection allows for the integration of energy derived from lipids and proteins into the citric acid cycle through its conversion to succinyl-CoA.
• Discuss the role of vitamin B12 in the metabolism of propionyl-CoA and its implications for overall energy production.
  • Vitamin B12 plays a vital role in the metabolism of propionyl-CoA by acting as a cofactor for the enzyme methylmalonyl-CoA mutase, which catalyzes the conversion of propionyl-CoA to succinyl-CoA. This reaction is essential for linking propionate metabolism to the citric acid cycle, enabling further energy extraction from nutrients. A deficiency in vitamin B12 can lead to impaired propionyl-CoA metabolism, disrupting overall energy production and potentially leading to metabolic disorders.
• Evaluate the consequences of impaired propionyl-CoA metabolism on human health, especially in relation to metabolic disorders.
  • Impaired metabolism of propionyl-CoA can lead to significant health issues, such as propionic acidemia. This genetic disorder results from deficiencies in enzymes involved in the conversion of propionyl-CoA to succinyl-CoA, causing an accumulation of propionic acid in the body. The buildup can result in metabolic acidosis, neurological deficits, and other systemic complications. Understanding these consequences emphasizes the importance of proper metabolic functioning and nutrient balance in maintaining human health.

Related terms

Succinyl-CoA: Succinyl-CoA is a four-carbon intermediate in the citric acid cycle that plays a key role in energy production and biosynthesis.

Odd-chain fatty acids: Odd-chain fatty acids are fatty acids that contain an odd number of carbon atoms, which are metabolized to yield propionyl-CoA.

Methylmalonyl-CoA: Methylmalonyl-CoA is an intermediate in the conversion of propionyl-CoA to succinyl-CoA, catalyzed by the enzyme methylmalonyl-CoA mutase.