Propionyl-CoA

Propionyl-CoA is a significant intermediate in the metabolic pathway known as the tricarboxylic acid cycle (TCA cycle) or Krebs cycle. It is derived from the catabolism of odd-chain fatty acids, branched-chain amino acids, and from the side chain of cholesterol.

Structure

Propionyl-CoA is a Coenzyme A (CoA) derivative in which the terminal sulfhydryl group (-SH) is linked to the carboxyl group (-COOH) of propionic acid through a high-energy thioester bond. The molecule is composed of an adenosine 3',5'-bisphosphate moiety, a pantothenic acid moiety, and a cysteamine moiety.

Metabolism

Propionyl-CoA is metabolized in a series of reactions known as the propionyl-CoA carboxylase pathway. This pathway converts propionyl-CoA to methylmalonyl-CoA, which is then converted to succinyl-CoA, a key intermediate in the TCA cycle. The conversion of propionyl-CoA to succinyl-CoA requires several enzymes and cofactors, including biotin, adenosylcobalamin, and methylmalonyl-CoA mutase.

Clinical significance

Defects in the metabolism of propionyl-CoA can lead to several metabolic disorders, including propionic acidemia and methylmalonic acidemia. These disorders are characterized by the accumulation of propionyl-CoA and its metabolites in the body, leading to various symptoms such as developmental delay, intellectual disability, and metabolic acidosis.

See also

• Coenzyme A
• Tricarboxylic acid cycle
• Propionic acidemia
• Methylmalonic acidemia