ketoacid

A ketoacid, or alpha-keto acid, is an organic compound that contains both a ketone group and a carboxylic acid group. The general structure is R-CO-COOH, with the ketone located at the alpha position relative to the carboxyl group. In biochemistry, alpha-keto acids most often arise from amino acid transamination, producing the corresponding keto acid and an amino acid.

Common examples include pyruvic acid (2-oxopropanoic acid), the simplest alpha-keto acid; and physiologically important members such as oxaloacetic acid (2-oxosuccinic acid) and alpha-ketoglutaric acid (2-oxoglutaric acid), which are intermediates of central metabolism. These compounds differ in the carbon skeleton attached to the alpha-keto carbon but share the characteristic adjacent ketone and carboxylate groups.

Biological role and metabolism: Alpha-keto acids are central in amino acid catabolism. Transaminases transfer the amino group from an amino acid to an acceptor such as alpha-ketoglutarate, yielding a corresponding alpha-keto acid and glutamate. The resulting alpha-keto acids can be further processed by oxidative decarboxylation to enter the citric acid cycle, or in some cases be used for gluconeogenesis. Pyruvate links carbohydrate metabolism to energy production and glucose synthesis; oxaloacetate and alpha-ketoglutarate are key intermediates of the TCA cycle.

Clinical relevance: Abnormal levels or accumulation of specific alpha-keto acids can indicate metabolic disturbances. For example, branched-chain alpha-keto acids accumulate in maple syrup urine disease due to deficient branched-chain alpha-ketoacid dehydrogenase, illustrating the diagnostic value of monitoring these compounds.