Proteoglycans

PROTEOGLYCANS


  • Proteoglycans are carbohydrates to which small amount of protein is attached.
  • Proteoglycans consists of 2. 95 % of carbohydrate and < 57% of protein.

Structure  of  proteoglycans:

  • All  of  the  glycosaminoglycans  (except  for  hyaluronic  acid)  are  attached  covalently to  protein  (called  core  protein)
  • Proteoglycans = glycosaminoglycans (mucopolysaccharides) + Core protein.
  • Proteoglycan monomer consists of core protein to which linear glycosaminoglycan chain is covalently attached.
  • The chains of glycosaminoglycan (composed  of upto 100 monosaccharides, i.e. upto 50 disaccharide units) extend out from core protein giving an appearance of bottle brush.
  • The core proteins of proteoglycan monomers are attached to hyaluronic acid by non-covalent electrostatic (ionic) bonds in  which  a linkprotein  participates.
  • Aggrecan, one of the important proteoglycan aggregate, is the major type found in cartilage.
  • The proteoglycan aggregatges are polyanionic, because of the many negative charges of the carboryl groups attached to some of the sugars.
  • These groups attract water molecules and hold, large amounts to form a hydrated gel like matrix that forms the body’s ground substance.
  • Ground substance along with fibrous structural proteins (collagen, elastin) and adhesive proteins (fibronectin) make up the extracellular matrix (ECM).
  • Exracellular matrix (ECM) = Ground substance (Proteoglycans + water) + Fibrous structural proteins + Adhesive proteins.

There are six classes of proteoglycans :

  1. Hyaluronic acid,
  2. chondroitin sulphates
  3. Keratan sulphate,
  4. dermatan sulphate,
  5. heparin
  6. heparan sulphate.
  • Keratan Sulphate is the only proteoglycan that does not contain acid sugar in disaccharide repeat unit.
  • Hyaluronic acid is the only proteoglycan that does not have core protein, i.e. glycosaminoglycan chain is not attached to core Protein.
  • Hyaluronic acid is the only proteoglycan without sulphate group. it is distributed in Synovial fluid which provides viscosity, vitreous humor. loose connective tissue.

Exam Important

  • Proteoglycan monomer consists of core protein to which linear glycosaminoglycan chain is covalently attached.
  • Proteoglycan monomer consists of core protein to which linear glycosaminoglycan chain is covalently attached.
  • The chains of glycosaminoglycan (composed  of upto 100 monosaccharides, i.e. upto 50 disaccharide units) extend out from core protein giving an appearance of bottle brush.
  • The core proteins of proteoglycan monomers are attached to hyaluronic acid by non-covalent electrostatic (ionic) bonds in  which  a linkprotein  participates.
  • Aggrecan, one of the important proteoglycan aggregate, is the major type found in cartilage.
  • The proteoglycan aggregatges are polyanionic, because of the many negative charges of the carboryl groups attached to some of the sugars.
  • These groups attract water molecules and hold, large amounts to form a hydrated gel like matrix that forms the body’s ground substance.
  • Ground substance along with fibrous structural proteins (collagen, elastin) and adhesive proteins (fibronectin) make up the extracellular matrix (ECM).
  • Exracellular matrix (ECM) = Ground substance (Proteoglycans + water) + Fibrous structural proteins + Adhesive proteins.
  • Hyaluronic acid is the only proteoglycan without sulphate group. it is distributed in Synovial fluid which provides viscosity, vitreous humor. loose connective tissue.
Don’t Forget to Solve all the previous Year Question asked on PROTEOGLYCANS

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