GLYCOSAMINO GLYCANS
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This document discusses glycosaminoglycans (GAGs), which are heteropolysaccharides composed of long chains of disaccharide units. It describes 8 properties that can differ between GAGs, including chain length, amino acid and uronic acid composition, and sulfate group attachment. The document then lists 9 functions of GAGs in the extracellular matrix and tissues, such as structural support, selective permeability, and shock absorption. Finally, it classifies and describes the characteristics and functions of 6 major GAGs: chondroitin sulfate, hyaluronic acid, dermatan sulfate, heparin, heparan sulfate, and keratan sulfate.
GLYCOSAMINO GLYCANS
- 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 distribution of GAG. 2
- 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) 3
- 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) 4
- 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. 5
- 6. 6 Amino sugar – D-Glucosamine or D-Galactosamine. Uronic acid – D-Glucuronic acid or L-Iduronic acid.
- 7. Classification 7 GAGS Sulphate free Sulphate containing Hyaluronic acid Chondrotin Sulphate Dermatan sulphate keratan sulphate Heparin Heparan Sulphate
- 8. 8 • Contains D-Glucoronic acid + Galactosamine. • Most abundant GAG in body. 1. Chondroitin sulfate
- 9. 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. 10
- 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. 11
- 12. 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 13
- 14. Present in skin, cardiac valves & tendon. Function : Present in sclera of eye where it has important function in maintaining overall shape of eye. 14
- 15. 4. Heparin 15 • Contains D-Glucuronic acid + Glucosamine • it is the only intracellular GAG.
- 16. 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. 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 18 • 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. 19
- 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. 21