Download Biochemistry of connective tissue

Biochemistry of
connective tissue.
FUNCTIONS of connective
tissue
•
•
•
•
•
Transport
Immunological defense
Mechanical support
Growth and repair
Haemopoiesis
Collagen is the major structural protein of
vertebrate extracellular matrix.
Types of collagen
Collagen type I
i)The fibers have diameter between 80 to 160nm.
ii)Found in bone, dentin, skin, tendon, muscles and walls of blood vessels.
Collagen type II
i)have a diameter <80nm
ii)found in invertiberal discs and hyaline cartilage.
Collagen type III
i)Found in spleen, muscle, and aorta.
Collagen type IV
Found around different types of in the basement membranes and
muscles.
Collagen type V
It is found in embryonic cell cultures and the basement membranes.
Collagen type VI
It is found in muscle and skin.
SCANNING ELECTRON MICROGRAPH OF DENSE
COLLAGEN FIBERS OF GINGIVA
Collagen acts as the support
structure in tissues
and facilitates the live and
function of cells.
HEALTHY GINGIVA
CONTAINS MANY
FIBROBLASTS AND A
FEW INFLAMMATORY
CELLS SUCH AS
MACROPHAGES
,NEUTROPHILS, PLASMA
CELLS AND
LYMPHOCYTES.
Collagen
• a. protein high in
content of AA,
glycine, proline,
hydroxyproline and
many AA missing
• b. Protein helix is
linearly oriented-3
chains twisted
around each other in
a fibril. H bonding
between the chains.
The hierarchical design of collagen.
The structural
features of
collagen ranges
from the amino
acid sequence,
tropocollagen
molecules,
collagen fibrils
to collagen
fibers.
• The tropocollagen cables are lined up
head-to-tail in rows that are
staggered by 64 nm along their long
axes and crosslinked at their ends to
improve strength
The synthesis of collagen molecules
Collagen molecules are
crosslinked into fibrils:
oxidative deamination
of hydroxylysine and
lysine forms reactive
aldehyde groups, which
link molecules together
(and also link α-chains
together too).
Collagen and elastin.
• Elastin polypeptide
chains are crosslinked together to
form rubberlike,
elastic fibers.
• Each elastin molecule
uncoils into a more
extended
conformation when
the fiber is tretched
and recoils
spontaneously as soon
as the stretching
force is relaxed.
Elastin is a protein in connective tissue that is
elastic and allows many tissues in the body to
resume their shape after stretching or
contracting.
• Elastin serves an
important function in
arteries and is
particularly abundant in
large elastic blood
vessels such as the
aorta. Elastin is also
very important in the
lungs, elastic ligaments,
the skin, the bladder,
elastic cartilage
• Elastin is primarily composed of the amino
acids glycine, valine, alanine, and proline. It is
a specialized protein with a molecular weight
of 64 to 66 kDa, and an irregular or random
coil conformation made up of 830 amino acids.
• Elastin is made by linking many soluble
tropoelastin protein molecules, in a reaction
catalyzed by lysyl oxidase, to make a massive
insoluble, durable cross-linked array. The
amino acid responsible for these cross-links is
lysine.
Desmosine and isodesmosine are both found in
elastin.
Proteoglycans
• Proteoglycans are proteins
modified by
glycosaminoglycans (GAG,
mucopolysaccharides).
• Glycosaminoglycans are
long-chain compounds made
up of hundreds repeating
disaccharide units. One of
the sugars in each
disaccharide unit is a
hexosamine (glycosamine).
• Many proteoglycans contain
a core protein which links
them to the cellular
membrane.
The four main types consist mainly of sulfated heparan
sulfate/heparin, chondroitin sulfate/dermatan, keratan sulfate,
and the non-sulfated glycosaminoglycan hyaluronic acid.
• Hyaluronic acid is
an extremely long
and rigid
glycosaminoglycan
• contains several
thousand sugars but
no protein core
• Linker molecules join
proteoglycans to
hyaluronic acid.
Disorders of connective tissue
•
•
Marfan syndrome - a
genetic disease causing
abnormal fibrillin.
Scurvy - dietary
deficiency in vitamin C,
leading to abnormal
collagen.
(hemorrhages, loose of teeth, gums
swell and bleed easily)
•
Ehlers-Danlos syndrome deficient type III collagen- a
genetic disease causing
progressive deterioration of
collagens, with different EDS
types affecting different sites
in the body, such as joints, heart
valves, organ walls, arterial
walls, etc.
• Osteogenesis Imperfecta
results in a dramatic
weakening in the structure of
bone, which leads to frequent
fractures occurring at an
early age. The fractures, in
turn, lead to permanent
deformaties of the
extremities.