Phenylpyruvic acid as a possible precursor of o-hydroxyphenylacetic acid in man.

The oral administration of phenylpyruvic acid to human subjects results in increased urinary excretion of o-hydroxyphenylacetic acid. This demonstrates that phenylpyruvic acid may act as a precursor for o-hydroxy derivatives of phenylalanine and suggests that the formation of o-tyrosine is not necessary to account for the excretion of o-hydroxyphenylacetic acid in phenylketonuria.