4-Hydroxyphenylpyruvic acid (4-HPPA) is an intermediate in the metabolism of the amino acid phenylalanine.

The aromatic side chain of phenylalanine is hydroxylated by the enzyme phenylalanine hydroxylase to form tyrosine.

[2] Additionally, 4-HPPA can be converted to homogentisic acid which is one of the precursors to ochronotic pigment.

[3] It is an intermediary compound in the biosynthesis of scytonemin.

This biochemistry article is a stub.