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GAGS

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  1. GLYCOSAMINO GLYCANS 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. • 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.

  3. 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)

  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)

  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.

  6. Amino sugar – D-Glucosamine or D-Galactosamine. Uronic acid – D-Glucuronic acid or L-Iduronic acid.

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

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

  9. 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.

  11. 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.

  12. 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.

  13. 3. Dermatan sulfate • Contains L-iduronic acid + Glucosamine

  14. Present in skin, cardiac valves & tendon. • Function : • Present in sclera of eye where it has important function in maintaining overall shape of eye.

  15. 4. Heparin • Contains D-Glucuronic acid + Glucosamine • it is the only intracellular GAG.

  16. 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.

  17. 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 • 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.

  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.