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 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 hippopotamuses. 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.

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 tyrosine.

4-Hydroxyphenylpyruvate 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. The conversion from tyr ...

(produced by transamination of tyrosine) is acted upon by the enzyme

4-hydroxyphenylpyruvate dioxygenase 4-Hydroxyphenylpyruvate dioxygenase (HPPD), also known as α-ketoisocaproate dioxygenase (KIC dioxygenase), is an Fe(II)-containing non-heme oxygenase that catalyzes the second reaction in the catabolism of tyrosine - the conversion of 4-hydro ...

to yield homogentisate. If active and present, the enzyme homogentisate 1,2-dioxygenase further degrades homogentisic acid to yield

4-maleylacetoacetic acid 4-Maleylacetoacetate (4-maleylacetoacetatic acid) is an intermediate in the metabolism of tyrosine. It is converted to fumarylacetoacetate by the enzyme 4-maleylacetoacetate cis-trans-isomerase. Gluthathione coenzymatically helps in conversion to ...

References

{{DEFAULTSORT:Homogentisic Acid Hydroquinones Acetic acids Hydroxy acids