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Urocanic

Urocanic, typically referring to urocanic acid, is a metabolite derived from the amino acid histidine. In humans and many mammals, urocanic acid is a natural constituent of the skin, especially the stratum corneum, where it accumulates from the breakdown of filaggrin and other histidine-containing proteins during epidermal differentiation. It is produced along the histidine catabolic pathway by the action of histidine ammonia-lyase on histidine, yielding urocanic acid, which can be further metabolized to other compounds in the pathway.

Urocanic acid exists mainly as trans-urocanic acid in undisturbed skin. When the skin is exposed to ultraviolet

Biological and clinical relevance: Trans-UCA absorbs UV light and contributes to the skin's natural photoprotection by

In addition to its photobiological roles, urocanic acid is a common laboratory and research target as a

radiation,
particularly
UVB,
trans-urocanic
acid
isomerizes
to
cis-urocanic
acid.
This
photochemical
change
is
a
well-established
phenomenon
and
has
drawn
attention
for
its
potential
biological
effects.
filtering
part
of
the
UV
spectrum.
Cis-UCA
has
been
studied
for
its
immunomodulatory
properties,
including
suppression
of
certain
immune
responses
in
the
skin,
which
has
been
implicated
in
UV-induced
immunosuppression
and
research
on
photocarcinogenesis.
The
exact
role
of
UCA
in
human
health
remains
a
topic
of
investigation,
with
ongoing
debate
about
the
significance
of
cis-UCA
in
vivo.
biomarker
for
UV
exposure
and
skin
metabolism.
It
is
also
encountered
in
dermatological
studies
of
keratinization
and
barrier
function.