Home

Homogentisate

Homogentisate, or homogentisic acid, is an intermediate in the catabolism of the aromatic amino acids tyrosine and phenylalanine. In humans and many other organisms, it is formed from p-hydroxyphenylpyruvate by the enzyme p-hydroxyphenylpyruvate dioxygenase as part of the tyrosine degradation pathway.

Under normal conditions, homogentisate is converted by homogentisate 1,2-dioxygenase to maleylacetoacetate, which is further processed to

Deficiency of homogentisate 1,2-dioxygenase leads to alkaptonuria, a rare inherited disorder characterized by accumulation of homogentisate

Chemically, homogentisic acid is a dihydroxyphenylacetic acid (often described as 2,5-dihydroxyphenylacetic acid) that exists as the

fumarylacetoacetate
and
eventually
to
fumarate
and
acetoacetate.
These
products
feed
into
central
metabolism.
The
proper
function
of
this
pathway
is
essential
for
efficient
breakdown
of
tyrosine-derived
compounds.
in
tissues
and
urine.
Urine
darkens
upon
standing
or
exposure
to
air
due
to
oxidation
and
polymerization
of
homogentisate.
Chronic
tissue
deposition
can
cause
ochronosis,
with
pigmentary
changes
in
cartilage,
skin,
and
connective
tissue
and
progressive
joint
or
spine
degeneration.
homogentisate
anion
at
physiological
pH.
It
can
form
various
salts
and
undergo
oxidative
polymerization
to
form
pigmented
deposits
observed
in
alkaptonuria.
The
compound
is
a
key
substrate
in
enzymatic
assays
of
the
tyrosine
degradation
pathway.