Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a

phenolic acid Phenolic acids or phenolcarboxylic acids are types of aromatic acid compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function (C6-C1 skeleton). Two important naturally occurring types of ...

usually found in ''

Arbutus unedo ''Arbutus unedo'' is an evergreen shrub or small tree in the family Ericaceae, native to the Mediterranean region and western Europe. The tree is well known for its fruits, which bear some resemblance to the strawberry — hence the common name ...

'' (strawberry-tree) honey. It is also present in the bacterial plant pathogen ''Xanthomonas campestris'' pv. ''phaseoli'' as well as in the yeast ''

Yarrowia lipolytica ''Yarrowia'' is a fungal genus in the family Dipodascaceae. For a while the genus was monotypic, containing the single species ''Yarrowia lipolytica'', a yeast that can use unusual carbon sources, such as hydrocarbons. This has made it of interes ...

'' where it is associated with the production of brown pigments. It is oxidatively dimerised to form

hipposudoric acid Hipposudoric acid is a red pigment found in the skin secretions of the hippopotamus; although the secretions are often known as "blood sweat" (thus the name "hipposudoric", referring to "hippo sweat"), they are neither blood nor sweat. Like its o ...

, one of the main constituents of the 'blood sweat' of

hippopotamus The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extan ...

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

William Prout William Prout FRS (; 15 January 1785 – 9 April 1850) was an English chemist, physician, and natural theologian. He is remembered today mainly for what is called Prout's hypothesis. Biography Prout was born in Horton, Gloucestershire in 1 ...

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 -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 ...

, consequently associated with

alkaptonuria Alkaptonuria is a rare inherited genetic disease which is caused by a mutation in the ''HGD'' gene for the enzyme homogentisate 1,2-dioxygenase (); if a person inherits an abnormal copy from both parents (it is a recessive condition), the body ac ...

Intermediate

It is an intermediate in the

catabolism Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, ...

of aromatic amino acids such as

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 ...

and

. 4-Hydroxyphenylpyruvate (produced by

transamination Transamination is a chemical reaction that transfers an amino group to a ketoacid to form new amino acids. This pathway is responsible for the deamination of most amino acids. This is one of the major degradation pathways which convert essential a ...

of tyrosine) is acted upon by the enzyme 4-hydroxyphenylpyruvate dioxygenase to yield homogentisate. If active and present, the enzyme

homogentisate 1,2-dioxygenase Homogentisate 1,2-dioxygenase (homogentisic acid oxidase, homogentisate oxidase, homogentisicase) is an enzyme which catalyzes the conversion of homogentisate to 4-Maleylacetoacetate, 4-maleylacetoacetate. Homogentisate 1,2-dioxygenase or HGD ...

further degrades homogentisic acid to yield 4-maleylacetoacetic acid.

References

{{DEFAULTSORT:Homogentisic Acid Hydroquinones Acetic acids Hydroxy acids