Alpha-keto acids, Alpha-ketoacids, or 2-oxoacids, such as pyruvic acid, have the keto group adjacent to the carboxylic acid. One important alpha-keto acid is oxaloacetic acid, a component of the Krebs cycle. Another is alpha-ketoglutarate, a 5-carbon ketoacid derived from glutamic acid. Alpha-ketoglutarate participates in cell signaling by functioning as a coenzyme, and is commonly used in transamination reactions. Alpha-keto acids possesses extensive chemistry as acylation agents.
Beta-keto acids, Beta-ketoacids, or 3-oxoacids, such as acetoacetic acid, have the ketone group at the second carbon from the carboxylic acid. They can be formed by the Claisen condensation.
Gamma-keto acids, Gamma-ketoacids, or 4-oxoacids, such as levulinic acid, have the ketone group at the third carbon from the carboxylic acid.
Keto acids appear in a wide variety of anabolic pathways in metabolism, across living organisms. For instance, in plants (specifically, in hemlock, pitcher plants, and fool's parsley), 5-oxo-octanoic acid is converted in enzymatic and non-enzymatic steps into the cyclic class of coniinealkaloids.
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