glycosamino glycans n.
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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.
slide6

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

slide8

1. Chondroitin sulfate

  • Contains D-Glucoronic acid + Galactosamine.
  • Most abundant GAG in body.
slide9

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.
slide11

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
slide14

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.
slide16

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.
slide19

Found in cornea & tendon.

  • 2 types :
  • Keratan sulfate І – cornea
  • Keratan sulfate ІІ – skeletal muscle
  • Function :
  • Maintains the corneal transparency.
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.