GLYCOSAMINO GLYCANS

GLYCOSAMINO GLYCANS are Heteropolysaccharides, containing uronic acid and amino sugars.

1. M.Prasad Naidu
MSc Medical Biochemistry,
Ph.D.Research Scholar

2. GLYCOSAMINO GLYCANS
They differ form each other in a number of the
following properties.
1. Chain length.
2.Amino –Acid composition.
3.Uronic –Acid composition.
4.Linkages between these components.
5.Presence or absence of sulfate groups.
6.The attachment of sulfate to sugar molecule.
7.The nature of core protein linked to GAG.
8.The tissue and sub. Cellular distributionof GAG.
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3. FUNCTIONS OF GAG
1.Structural component of extra cellular
matrix.
2.Contribute to the turgor of various tissues.
3.Acts as sieves in EC matrix
4.Facilitate cell migration,acts as shock
absorber at joints,(HA)
5.Maintenance of compressibility of
cartilage(HA&CS)
6.Have a structural role in sclera & in corneal
transparency (KS1,DS)
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4. FUNCTIONS OF GAG
CONT-----
7. Acts as anticoagulant (HA)
8. Determines the charge selectiveness of
renal glomerulus.(HS)
9. Formation of cell membrane and synaptic
vesicles (HS)
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5. Glycosaminoglycans / GAGS
or Mucopolysaccharides
Are large complex of –ve charged (carboxy & sulfate
groups) heteropolysaccharide chain generally associated
with a small amount of protein -proteoglycan.
Special ability to bind large amount of water producing gel
like matrix, that forms the bodies ground substance.
Unbranched, long repeating diasaccharide Contains uronic
acid & amino sugars.
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6. 6
Amino sugar –D-Glucosamine or D-Galactosamine.
Uronic acid –D-Glucuronic acid or L-Iduronic acid.

7. Classification
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GAGS
Sulphate free Sulphate containing
Hyaluronic acid
Chondrotin Sulphate
Dermatan sulphate
keratan sulphate
Heparin
Heparan Sulphate

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•Contains D-Glucoronic acid + Galactosamine.
•Most abundant GAG in body.
1. Chondroitin sulfate

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Widely distributed in bone, cartilage & tendons.
Function :
In cartilage, it binds collagen & hold fibers in a tight
strong network.
Role in Compressibility of cartilage in weight bearing
along with Hyaluronic acid.
2 types of chondroitin sulfate :
Sulphated at C 4 or C 6 group.

10. 2. Hyaluronic acid
Contains D-Glucoronic acid + Glucosamine.
It is sulphate free GAG.
It is sulphate free GAG.
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11. Ground substance of synovial fluid of joints, vitreous
humor of eyes and connective tissues, tendon.
Hyaluronidaseis an enzyme that breaks β-1 –4 linkages.
Present in high concentration in testes, seminal fluid, &
in certain snake and insect venoms.
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Functions of Hyaluronic acid
Serves as a lubricant and shock absorbant in joints.
Determines charge selectiveness of renal glomerulus.
Acts as seives in extracelluar matrix.
Permits cell migration during morphogenesis & wound repair.
Hyaluronidaseenzyme of semen degrades the gel around ovum
& allows effective penetration of sperm into ovum.

13. 3. Dermatansulfate
Contains L-iduronic acid + Glucosamine
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14. Present in skin, cardiac valves & tendon.
Function :
Present in sclera of eye where it has important function
in maintaining overall shape of eye.
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15. 4. Heparin
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•Contains D-Glucuronic acid + Glucosamine
•it is the only intracellular GAG.

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It is an anticoagulant(prevents blood clotting )
Found in granules of mast cells that line the arteries of
lung, liver, kidney, spleen.
Strongly acidic due to presence of more sulphate group.
Heparin helps in the release of the enzyme lipoprotein lipase.
Helps to clear the lipidemia after fatty meal –also called clearing
factor.

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5. Heparan sulfate
Same as heparin except some amino groups carry acetyl
group & % of Sulphate groups are smaller.
It is extracellular GAG .
Present in basement membrane & as a ubiquitous
component of cell surface.

18. 6. Keratan sulfate
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•contains D-Galactose + Glucosamine
•Only GAG with no uronic acid.

19. Found in cornea & tendon.
2 types :
Keratan sulfate І–cornea
Keratan sulfate ІІ–skeletal muscle
Function :
Maintains the corneal transparency.
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20. 20
Proteoglycan

21. Heteropolysaccharide
Agar :
Contains galactose , glucose & other sugars.
Cannot be digested by bacteria.
So used as supporting agent to culture bacterial colonies.
Also as support medium of immuno diffusion &
immuno-electrophoresis.
Agarose:
galactose & 3,6 anhydro galactose units
Used as matrix for electrophoresis.
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