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

phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...

. The aromatic side chain of phenylalanine is hydroxylated by the enzyme

phenylalanine hydroxylase Phenylalanine hydroxylase. (PAH) () is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine. PAH is one of three members of the biopterin-dependent aromatic amino acid hydroxylases, a class ...

to form

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...

. The conversion from tyrosine to 4-HPPA is in turn catalyzed by

tyrosine aminotransferase Tyrosine aminotransferase (or tyrosine transaminase) is an enzyme present in the liver and catalyzes the conversion of tyrosine to 4-hydroxyphenylpyruvate. L-tyrosine + 2-oxoglutarate \rightleftharpoons 4-hydroxyphenylpyruvate + L-glutamate ...

. Additionally, 4-HPPA can be converted to

homogentisic acid Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in ''Arbutus unedo'' (strawberry-tree) honey. It is also present in the bacterial plant pathogen ''Xanthomonas campestris'' pv. ''phaseoli'' as well as in the ye ...

which is one of the precursors to

ochronotic pigment Ochronosis is a syndrome caused by the accumulation of homogentisic acid in connective tissues. The condition was named after the yellowish (ocher-like) discoloration of the tissue seen on microscopic examination. Macroscopically, though, the a ...

. It is an intermediary compound in the biosynthesis of

scytonemin Scytonemin is a secondary metabolite and an Extracellular matrix, extracellular matrix (sheath) Biological pigment, pigment synthesized by many strains of cyanobacteria, including ''Nostoc'', ''Scytonema'', Calothrix crustacea, ''Calothrix'', ''Lyn ...

References

Natural phenols Phenols Alpha-keto acids Propionic acids Hydroxy acids {{biochem-stub

See also

References