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5hydroxylysine

5-hydroxylysine is a hydroxylated form of the essential amino acid lysine. It is best known as a post-translational modification that occurs in collagen and other extracellular matrix proteins, where specific lysine residues are hydroxylated at the ε-position of the side chain to form 5-hydroxylysine.

Biosynthesis and chemical basis: The conversion of lysine to hydroxylysine is catalyzed by lysyl hydroxylase enzymes,

Function in collagen cross-linking: Hydroxylysine residues can undergo further processing to generate aldehyde groups via lysyl

Biological significance and measurement: In addition to structural roles, hydroxylysine-containing cross-links are commonly used as biomarkers

See also: hydroxylysine, 4-hydroxylysine, collagen cross-links.

typically
in
the
endoplasmic
reticulum
of
collagen-producing
cells.
The
reaction
requires
iron(II),
molecular
oxygen,
alpha-ketoglutarate,
and
ascorbate
(vitamin
C)
as
cofactors.
This
modification
changes
the
chemical
properties
of
lysine
residues
and
primes
them
for
subsequent
glycosylation
and
cross-link
formation.
oxidase,
which
participate
in
covalent
cross-linking
between
collagen
molecules.
Cross-links
formed
from
hydroxylysine-derived
residues,
such
as
hydroxylysyl
pyridinoline
and
related
structures,
contribute
to
the
stability
and
tensile
strength
of
the
collagenous
matrix.
The
presence
of
5-hydroxylysine
is
therefore
a
key
determinant
of
collagen
maturation
and
mechanical
properties.
of
collagen
turnover
and
bone
remodeling.
Analytical
methods
detect
hydroxylysine
and
related
cross-links
in
tissues,
plasma,
or
urine,
typically
by
chromatography
and
mass
spectrometry.
Defects
in
lysyl
hydroxylation
can
lead
to
connective
tissue
abnormalities
and
related
disorders.