Glycosamino glycans
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GAGS

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Glycosamino glycans

GLYCOSAMINO GLYCANS

M.Prasad Naidu

MSc Medical Biochemistry,

Ph.D.Research Scholar


Glycosamino glycans1

GLYCOSAMINO GLYCANS

They differ form each other in a number of the following properties.

  • Chain length.

  • Amino – Acid composition.

  • Uronic – Acid composition.

  • Linkages between these components.

  • Presence or absence of sulfate groups.

  • The attachment of sulfate to sugar molecule.

  • The nature of core protein linked to GAG.

  • The tissue and sub. Cellular distribution of GAG.


Functions of gag

FUNCTIONS OF GAG

  • Structural component of extra cellular matrix.

  • Contribute to the turgor of various tissues.

  • Acts as sieves in EC matrix

  • Facilitate cell migration,acts as shock absorber at joints,(HA)

  • Maintenance of compressibility of cartilage(HA&CS)

  • Have a structural role in sclera & in corneal transparency (KS1,DS)


Functions of gag cont

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)


Glycosaminoglycans gags or mucopolysaccharides

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.


Gags

Amino sugar – D-Glucosamine or D-Galactosamine.

Uronic acid – D-Glucuronic acid or L-Iduronic acid.


Classification

Classification

GAGS

Sulphate free

Sulphate containing

Chondrotin Sulphate

Dermatan sulphate

keratan sulphate

Heparin

Heparan Sulphate

Hyaluronic acid


Gags

1. Chondroitin sulfate

  • Contains D-Glucoronic acid + Galactosamine.

  • Most abundant GAG in body.


Gags

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.


2 hyaluronic acid

2. Hyaluronic acid

  • Contains D-Glucoronic acid + Glucosamine.

  • It is sulphate free GAG.

  • It is sulphate free GAG.


Gags

  • Ground substance of synovial fluid of joints, vitreous humor of eyes and connective tissues, tendon.

  • Hyaluronidase is an enzyme that breaks β-1 – 4 linkages.

  • Present in high concentration in testes, seminal fluid, & in certain snake and insect venoms.


Functions of hyaluronic acid

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.

  • Hyaluronidase enzyme of semen degrades the gel around ovum & allows effective penetration of sperm into ovum.


3 dermatan sulfate

3. Dermatan sulfate

  • Contains L-iduronic acid + Glucosamine


Gags

  • Present in skin, cardiac valves & tendon.

  • Function :

  • Present in sclera of eye where it has important function in maintaining overall shape of eye.


4 heparin

4. Heparin

  • Contains D-Glucuronic acid + Glucosamine

  • it is the only intracellular GAG.


Gags

  • 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.


5 heparan sulfate

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.


6 keratan sulfate

6. Keratan sulfate

  • contains D-Galactose + Glucosamine

  • Only GAG with no uronic acid.


Gags

  • Found in cornea & tendon.

  • 2 types :

  • Keratan sulfate І – cornea

  • Keratan sulfate ІІ – skeletal muscle

  • Function :

  • Maintains the corneal transparency.


Gags

Proteoglycan


Heteropolysaccharide

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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