Homogentisic acid

Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in Arbutus unedo (strawberry-tree) honey.^[1] It is also present in the bacterial plant pathogen Xanthomonas campestris pv. phaseoli^[2] as well as in the yeast Yarrowia lipolytica^[3] where it is associated with the production of brown pigments. It is oxidatively dimerised to form hipposudoric acid, one of the main constituents of the 'blood sweat' of hippopotamuses.

Homogentisic acid

Names
Preferred IUPAC name (2,5-Dihydroxyphenyl)acetic acid
Other names Melanic acid
Identifiers
CAS Number	451-13-8 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:44747 Y
ChemSpider	759 Y
DrugBank	DB08327 Y
ECHA InfoCard	100.006.540
KEGG	C00544 Y
MeSH	Homogentisic+acid
PubChem CID	780
UNII	NP8UE6VF08 Y
CompTox Dashboard (EPA)	DTXSID1060005
InChI InChI=1S/C8H8O4/c9-6-1-2-7(10)5(3-6)4-8(11)12/h1-3,9-10H,4H2,(H,11,12) Y Key: IGMNYECMUMZDDF-UHFFFAOYSA-N Y InChI=1/C8H8O4/c9-6-1-2-7(10)5(3-6)4-8(11)12/h1-3,9-10H,4H2,(H,11,12) Key: IGMNYECMUMZDDF-UHFFFAOYAK
SMILES O=C(O)Cc1cc(O)ccc1O
Properties
Chemical formula	C8H8O4
Molar mass	168.148 g·mol−1
Melting point	150 to 152 °C (302 to 306 °F; 423 to 425 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

It is less commonly known as melanic acid, the name chosen by William Prout.

Human pathology

Accumulation of excess homogentisic acid and its oxide, named alkapton, is a result of the failure of the enzyme homogentisic acid 1,2-dioxygenase (typically due to a mutation) in the degradative pathway of tyrosine, consequently associated with alkaptonuria.^[4]

Intermediate

It is an intermediate in the catabolism of aromatic amino acids such as phenylalanine and tyrosine.

4-Hydroxyphenylpyruvate (produced by transamination of tyrosine) is acted upon by the enzyme 4-hydroxyphenylpyruvate dioxygenase to yield homogentisate.^[5] If active and present, the enzyme homogentisate 1,2-dioxygenase further degrades homogentisic acid to yield 4-maleylacetoacetic acid.^[6]