phenylpyruvate

Phenylpyruvate, also known as phenylpyruvic acid, is an organic compound that functions as an alpha-keto acid and a metabolite in the catabolism of the essential amino acid phenylalanine. Its chemical formula is C9H8O3, and its structure consists of a phenyl group attached to a CH2 group that bears a keto at the alpha position and a carboxyl group (Ar-CH2-CO-CO2H).

Biosynthesis and metabolism: In many organisms, phenylalanine can undergo transamination, transferring its amino group to an α-ketoglutarate to form phenylpyruvate and glutamate. Aromatic amino acid transaminases mediate this reaction. Phenylpyruvate can be further processed by decarboxylation to phenylacetaldehyde and then oxidation to phenylacetic acid; it can also be reduced to phenyllactate. These routes reflect its role as a metabolic crossroads in phenylalanine catabolism.

Physiological and clinical relevance: Phenylpyruvate is a normal intermediate in phenylalanine metabolism, but its accumulation is associated with disorders of phenylalanine processing. In phenylketonuria (PKU), deficiency of phenylalanine hydroxylase leads to elevated phenylalanine levels, which are diverted into transamination and result in increased phenylpyruvate and downstream metabolites such as phenylacetate and phenyllactate. These metabolites can be excreted in urine and contribute to the metabolic phenotype observed in PKU. Detection of these compounds has historically aided diagnostic screening.

See also: phenylalanine, phenylpyruvate metabolism, phenylacetate.