Heteropolyseccharide

Dr. waseem kausarI M D C

biochemistry

Heteropolysaccharides (Heteroglycan)mucopolysaccharides(glycosaminoglycans)

• COMPLEX CARBOHYDRATES(different types of monosaccharides or their derivatives)

• usually composed of AMINO SUGARS (hexosamine)& URONIC ACID units as principal components

• some are composed of AMINO SUGARS without uronic acids

• These are essential component of tissues, either free or with proteins

• Provide ground substance• Having more OH groups and – ve charge on them,

holding large quantity of water so having cushioning or lubricating other structures.

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Conti-

• Glycoproteins protein (> 96 % protein) with branched or unbranched oligosec-. carbohydrate < 4%. perform a variety of functions, which include enzymes, hormones, receptors, structural proteins and transport proteins.

• Proteoglycans or Mucoproteins or Mucoids. (GAG) They are those glycoprotein in which the carbohydrate > 4%.

Peptidoglycan• A rigid component of bact-

cell.• polymer of GlcNAc & MurAc.• Lies side by side, cross linked

by short peptides(provides strength and prevent cell swelling)

• Lysozymes

Agar• a mixture of sulfated

heteropolysaccharides made up of D-galactose and an L-galactose derivative ether-linked between C-3 and C-6 .

• cell walls marine red algae and seaweed.

• The two major components unbranched polymer agarose and a branched component, agaropectin.

• useful in the biochemistry laboratory.• When a suspension of agarose in

water is heated and cooled, the agarose forms a double helix: two molecules in parallel orientation twist together with a helix repeat of three residues; water molecules are trapped in the central cavity

Carbohydrates found in glycoprotein

Glycosaminoglycans

• special ability to bind large amounts of water, thereby producing the gel-like matrix that forms the basis of the body's ground substance, which, along with fibrous components such as collagen, make up the extracellular matrix.

• The viscous, lubricating properties of mucous secretions also result from the presence of glycosaminoglycans, which led to the original naming of these compounds as mucopolysaccharides.

MPS

• 1, Neutral• 2, Acidic

» a, sulphate free» b, sulphate containing

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Sulphate containing

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Chondroitin 4 and 6 sulphates

• Repeating D/s consisting of N-acetyl glucosamine & galactose

• No uronic acid• Keratan SO4 1( link b/w N-acetyl glucosamine

and aspargine is N- glycosidic)• Keratan SO411(link to protein is O- glycosidic)

• Found in cornea

Heparin• Anticoagulant• Produced by mast cells• Polymer of D –

glucosamine(N- Glu) and either of the two uronic acid D(Glc UA) or L(IDUA)

• Strongly acidic

Acidic sulphate free1, hyaluronic acid

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2, chondroitin

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It is found in cornea, also isolated in cranial cortilages, it contains N- acetyl galactosamine

Neutral MPS

• These contains peptides or amino acids with carbohydrates

• Four m/s are found in all types of Blood group substances .e.g galactose,fucos, acety- glucosamine and acety- galactoseamine.

polysaccharides can be linked to other molecules to form glyco-proteins and glyco-lipids

GlycoproteinsSome examples

• Polysaccharide component of antibodies has major effect on antibody function

• Polysaccharides attached to proteins on surface of red blood cells (RBC) determine blood type (A,B,O)

• Polysaccharides are attached to proteins in the Golgi apparatus through a process of post-translational modification

• Different types of cells do different post-tranlational modifications– More about this later

Glycolipids• Polysaccharides can also be attached to lipid molecules

•An outer-membrane constituent of gram negative bacteria, LPS, which includes O-antigen, a core polysaccharide and a Lipid A, coats the cell surface and works to exclude large hydrophobic compounds such as bile salts and antibiotics from invading the cell. O-antigen are long hydrophilic carbohydrate chains (up to 50 sugars long) that extend out from the outer membrane while Lipid A (and fatty acids) anchors the LPS to the outer membrane.

Glycolipids

• Polysaccharides (blue) are also used in animal cells to link surface proteins and lipid anchors to the membrane.