α-keto acid

Definition

An α-keto acid is an organic compound containing a ketone group (C=O) adjacent to a carboxyl group (COOH). These compounds are important intermediates in the catabolism of lipids and proteins, playing a crucial role in energy production and metabolism.

5 Must Know Facts For Your Next Test

1. α-Keto acids are key intermediates in the citric acid cycle, also known as the Krebs cycle, which is a central pathway for energy production in cells.
2. The oxidative decarboxylation of α-keto acids, such as pyruvate and α-ketoglutarate, is a critical step in the catabolism of carbohydrates, lipids, and proteins.
3. Transamination reactions involving α-keto acids and amino acids are essential for the interconversion of these biomolecules and the regulation of nitrogen balance in the body.
4. Deficiencies or imbalances in α-keto acid metabolism can lead to various metabolic disorders, such as maple syrup urine disease and homocystinuria.
5. α-Keto acids can also be used as substrates for the synthesis of other important biomolecules, such as neurotransmitters and hormones.

Review Questions

• Explain the role of α-keto acids in the catabolism of lipids and proteins.
  • α-Keto acids are central intermediates in the catabolic pathways of both lipids and proteins. In the catabolism of lipids, the oxidative decarboxylation of α-keto acids, such as pyruvate and acetyl-CoA, is a crucial step in the breakdown of fatty acids and the subsequent entry of their carbon skeletons into the citric acid cycle for energy production. Similarly, in the catabolism of proteins, the transamination of amino acids with α-keto acids, like α-ketoglutarate, leads to the formation of new amino acids that can then be further degraded, with the α-keto acid intermediates entering the citric acid cycle.
• Describe the importance of the citric acid cycle in the metabolism of α-keto acids.
  • The citric acid cycle, also known as the Krebs cycle, is a central metabolic pathway that is closely linked to the metabolism of α-keto acids. Many α-keto acids, such as pyruvate, acetyl-CoA, and α-ketoglutarate, are either directly produced as intermediates in the citric acid cycle or enter the cycle after undergoing various catabolic processes. The oxidation and decarboxylation of these α-keto acids within the citric acid cycle is a crucial step in the complete oxidation of carbohydrates, lipids, and proteins, ultimately leading to the generation of ATP, the primary energy currency of the cell. The citric acid cycle, therefore, plays a pivotal role in the efficient metabolism of α-keto acids and the overall energy production in the body.
• Analyze the potential consequences of imbalances or deficiencies in α-keto acid metabolism.
  • Disruptions in the metabolism of α-keto acids can have significant consequences for an individual's health and well-being. Deficiencies or imbalances in the metabolism of specific α-keto acids can lead to the accumulation of these compounds or the depletion of downstream metabolites, resulting in various metabolic disorders. For example, a deficiency in the enzyme responsible for the oxidative decarboxylation of α-ketoglutarate can lead to the condition known as maple syrup urine disease, characterized by the buildup of branched-chain α-keto acids and the associated neurological and developmental problems. Similarly, an imbalance in the metabolism of homocysteine, an α-keto acid intermediate, can contribute to the development of homocystinuria, which is linked to an increased risk of cardiovascular and neurological complications. Understanding the importance of proper α-keto acid metabolism is crucial for the prevention, diagnosis, and management of these metabolic disorders.

Related terms

Decarboxylation: The removal of a carboxyl group (COOH) from a molecule, often resulting in the release of carbon dioxide.

Transamination:

A biochemical reaction where an amino group is transferred from an amino acid to an α-keto acid, forming a new amino acid.

Oxidative decarboxylation: The process where an α-keto acid undergoes decarboxylation while being oxidized, producing a new compound with one less carbon atom.