HETEROPOLYSACCHARIDES/HETEROGLYCANS/MUCOPOLYSACCHARIDES

-Contain two / more different monosaccharides

-Heteropolysaccharides containing uronic acid (acidic unit) and amino sugar are called mucopolysacharrides or glycosaminoglycans.

-Because of charged groups, i.e., uronic acid and amino sugars, they attract water molecules producing viscous solutions.

-When these mucopolysaccharides are combined with proteins are called proteoglycans.

NEUTRAL MPS:

-Present in pneumococci capsule

-Type specificity of pneumococci depends on specific polysaccharide present on the capsule

-These capsular polysaccharides from pneumococci capsule in hydrolysis yield glucosamine and glucuronic acid.

 ACIDIC SULFATE FREE MPS

I.Hyaluronic acid:

-It is made of repeating units of N-acetyl glucosamine and D-glucuronic acid.

-Present in connective tissues, tendons, synovial fluid, vitreous humor, rheumatic nodule 

-Occurs in both free combination and salt like the combination with proteins

-Forms the ground substance of mesenchyme

-Hyaluronidase is an enzyme present in testicular tissue, spleen , pneumococci, and hemolytic streptococci, which catalyzes hyaluronic acid depolymerization, reducing viscosity and facilitates diffusion of material into tissue space. Hence it is also called a spreading factor.

II.Chondroitin

-It is made of repeating units of N-acetyl galactosamine and D-glucuronic acid

-Found in corne

- Isolated from cranial cartilage

 ACIDIC SULFATE CONTAINING MPS

I.Keratinosulphate :

-Made of repeating units of N-acetyl galactosamine and galactosamine

-Found in costal cartilage and cornea

-It is isolated from the bovine cornea.

-Present in nucleus pulposus and wall of the aorta'

-Two types:

--keratin sulfate 1: present in the cornea

--keratin sulfate 2: present in skeletal tissue

II.Chondroitin sulfate:

-Present in the ground substance of mammalian tissue and cartilage

-Occur in combination with proteins to form chondroproteins.

Four types :

Chondroitin sulfate A –

----Present in cartilage, adult bone, and cornea

----It is made of repeating units of N-acetyl D galactosamine and D glucuronic acid.

     Chondroitin sulfate B 

----Present in skin,cardiac valves, and tendons

----Isolated from aortic wall and lung parenchyma

----It is made of repeating units of N-acetyl D galactosamine and L glucuronic acid.

----It has weak anticoagulant property and so-called as β heparin

----It is also called dermatan sulfate as it is present in the skin.

----Sulfate moiety (SO4) is bonded at the C4 position of galactosamine.

----Chondroitin sulfate C 

----Found in cartilage and tendons

-----It is made of repeating units of N-acetyl D galactosamine and L glucuronic acid

----Sulfate moiety (SO4) is bonded at the C6 position of galactosamine.

----Chondroitin sulfate D

----Found in the cartilage of shark.

----The structure is similar to that of Chondroitin sulfate C except that SO4 attached is attached at 2^nd or 3^rd carbon of uronic acid moiety.

m  III.Heparin Sulfate

----Also called as α heparin

-----It is made of repeating units of D glucosamine and either of uronic acids, i.e. D glucuronic acid or L glucuronic acid.

-----Molecular weight – 17000 to 20000

-----Produced mainly by mast cells

-----It is an anticoagulant present in the liver

-----Also seen in the lungs, thymus, spleen, walls of large arteries, and skin

------It is strongly acidic due to the presence of sulphuric acid groups

      -NH2 (amino) group at C2 and –OH group at C6 of Dglucosamine and OH group of C2 of uronic acid, D glucuronic acid, and L iduronic acid are sulfated.