Glycoaminoglycans (GAGs) aka [Mucopolysaccharides]
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GAGs | Structure | Bonds / Linkage | Hydrolytic Products | Distribution | |
Hyaluronic acid | Glucuronic acid | N-acetyl glucosamine | Intraunit: β 1,3 glycosidic bond Interunit: β 1,4 linkages | 1. glucuronic acid 2. glucosamine 3. acetic acid | 1. synovial joint – lubricant 2. shock absorbent (vitreous body of eye) 3. cement substances (ECM between skin cells) |
Chondroitin sulfate | Glucoronic acid | N-acetyl galactosamine-S [S on C4 or C6] | Intraunit: β 1,3 Interunit: β 1,4 | 1. glucuronic acid 2. galactosamine 3. acetic acid 4. sulphuric acid | Cartilage, bone, heart valves, tendon (hard CT) |
Dermatan sulfate | L- Idurnic acid | N -acetyl galactosamine-S [S on C4] | Intraunit: β 1,3 Interunit: β 1,4 | 1. iduronic acid 2. galactosamine 3. acetic acid 4. sulphuric acid | Skin, blood vessels, heart valve |
Heparin | Glucoronic acid-S or Iduronic acid-S | Glucosamine-S-S [S on C2 & C6] | Intraunit:α 1,4 Interunit: α 1,4 | 1. glucuronic / iduronic acid 2. glucosamine 3. sulphuric acid | Mast cells’ granules, liver, kidney, lungs (acts as anti-coagulant) |
Heparan sulfate | Glucoronic acid-S or Iduronic acid-S | N-acetyl glucosamine-S OR Glucosamine-S-S [S on C2 & C6] | Intraunit: α 1,4 Interunit: α 1,4 | 1. glucuronic / iduronic acid 2. glucosamine 3. acetic acid 4. sulphuric acid | ECM of all tissues |
Keratan sulfate | Galactose | N-acetyl glucosamine-S [ S on C6 of either sugar] | Intraunit: β 1,4 Interunit: β 1,3 | 1. galactose 2. glucosamine 3. acetic acid 4. sulphuric acid | Cornea of the eye & skin, loose CT |
NB. Glycosidic linkage = glycosidic bond, use interchangeable both in intraunit and interunit.
Hydrolytic Products Comparison
Glucuronic acid | Iduronic acid | Galactose | Glucosamine | Galactosamine | Acetic acid | Sulphric acid | |
Hyaluronic acid | / | / | / | ||||
Chondroitin sulfate | / | / | / | / | |||
Dermatan sulfate | / | / | / | / | |||
Heparin | / | / | / | / * | |||
Heparan sulfate | / | / | / | / | / | ||
Keratin sulfate | / | / | / | / |
* most rich in sulphate among GAGs
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