Heteropolysaccharides are classified into three main categories: glycosaminoglycans (GAGs), glycoconjugates, and mucilage. GAGs include hyaluronic acid, chondroitin, keratan sulfate, dermatan sulfate, and heparin. They are long unbranched chains composed of repeating disaccharide units. Glycoconjugates include proteoglycans, glycoproteins, and glycolipids. Proteoglycans are GAGs covalently attached to core proteins. GAGs contribute to tissue structure and function through their hydrophilic and compressive properties. They also act as lubricants and barriers in tissues like cartilage.

1. Heteropolysaccharides
lec # 14- 18
Maria gul
Lecturer
Jips, Lahore

2. Heteropolysaccharide
classification
1.GAGS 2.glycoconjugates 3. mucilage
Natural proteoglycans agar
Acidic sulfate free
Hyaluranic acid, chondriotin
glycoprotein Vegetable gum
Sulfate containing
Keratan, heparin, chondriotin
glycolipids pectin

3. Glycosaminoglycan's
•Jeanloz has suggested the name Glycosaminoglycan's
(GAG) to describe this group of substances. They are
usually composed of amino sugar and uronic acid
units as the principal components, though some are
chiefly made up of amino sugar and monosaccharide
units without the presence of uronic acid. The
hexosamine present is generally acetylated. They are
essential components of tissues, where they are
generally present either in free form or in combination
with proteins. Carbohydrate content varies.

4. GAGS
• Glycosaminoglycan's (GAGs) are long, unbranched, hetero poly-
saccharide chains generally composed of a repeating disaccharide
unit
• [acidic sugar–amino sugar]n
• The amino sugar is either D-glucosamine or D-galactosamine, in
which the amino group is usually acetylated, thus eliminating its
positive charge
• The acidic sugar is either D-glucuronic acid or its C-5 epimer, L-
iduronic acid

5. Relationship between glycosaminoglycan structure
and function
•Because of their large number of negative charges,
these hetero-polysaccharide chains tend to be
extended in solution.
•They repel each other, and are surrounded by a shell of
water molecules. When brought together, they “slip”
past each other, much as two magnets with the same
polarity seem to slip past each other. This produces the
“slippery” consistency of mucous secretions and
synovial fluid.

6. • When a solution of glycosaminoglycan's is
compressed, the water is “squeezed out” and the
glycosaminoglycan's are forced to occupy a smaller
volume. When the compression is released, the
glycosaminoglycan's spring back to their original,
hydrated volume because of the repulsion of their
negative charges. This property contributes to the
resilience of synovial fluid and the vitreous humor of
the eye

8. classification of GAGS
• Acidic MPS
A. Sulfate free
1. Hyaluranic acid
2. Chondriotin
B. Sulfate containing
1. Keratan Sulphate
2. Chondroitin Sulphates
3. Heparin
Neutral MPS

9. Hyaluranic acid

10. Hyaluronidase:,
• An enzyme present in certain tissues, notably
testicular tissue and spleen.
• The enzyme catalyses the depolymerisation of
hyaluronic acid and by reducing its viscosity facilitates
diffusion of materials into tissue spaces.

12. Chondroitin
• Another sulphate free acid mucopolysaccharide.
• Found in cornea and has been isolated from cranial cartilages.
• It contains N-acetylgalactosamine and glucuronic acid.

13. Sulphate Containing Acid MPS
• 1. Keratan Sulphate (Kerato Sulphate)
• A sulphate containing acid MPS.
• Found in cornea has been isolated from bovine cornea.
• Composition: It is composed of repeating disaccharide
• unit consisting of N-acetyl glucosamine and galactose
• N-acetyl glucosamine→ Galactose → N-Acetyl glucosamine
• * fucose hexose deoxy sugar ( C6H12O5)

14. *N-Acetylneuraminic acid (Neu5Ac or NANA)
• 9 carbon amino sugar
• N-Acetylneuraminic acid (Neu5Ac or NANA) is the predominant sialic
acid found in human cells, and many mammalian cells. Other forms,
such as N-Glycolylneuraminic acid, may also occur in cells. This
residue is negatively charged at physiological pH and is found in
complex glycans on mucins and glycoproteins found at the cell
membrane. Neu5Ac residues are also found in glycolipids, known
as gangliosides, a crucial component of neuronal membranes found in
the brain. Along with involvement in preventing infections
(mucus associated with mucous membranes—mouth, nose, GI,
respiratory tract),

16. functions
• Role in corneal transparency:
• Keratan sulphate I is present in cornea of the eye

18. • Role in compressibility of cartilages: Chondroitin sulphates and
hyaluronic acid are present in high concentration in cartilages and
have a role in compressibility of cartilage in weight bearing.

19. • * a short band of tough, flexible fibrous connective tissue which
connects two bones or cartilages or holds together a joint.
• a membranous fold that supports an organ and keeps it in position.
• * Tendons are similar to ligaments; both are made of collagen.
Ligaments join one bone to bone, while tendons connect muscle to
bone for a proper functioning of the body.
•

21. Dermatan sulfate

22. functions
• Role in sclera of eye: Dermatan sulphate is present in sclera of the
eye where it has an important function in maintaining overall shape
of the eye.

23. Heparin

26. Neutral MPS
• Many of the neutral nitrogenous polysaccharides of various types are
found in pneumococci capsule. Type specificity of pneumococci
resides on specific polysaccharides present on capsule (“hapten”).
• Compostion: glucosamine and Glucuronic acids.
• Blood group substances

27. Glycoconjugates
• Proteoglycans
• Glycoproteins
• Glycolipids

28. Structure of proteoglycans
• All of the glycosaminoglycan's, except hyaluronic acid, are found
covalently attached to protein, forming proteoglycan monomers.
• Structure of proteoglycan monomers: A proteoglycan monomer
found in cartilage consists of a core protein to which the linear
glycosaminoglycan chains are covalently attached. These chains,
which may each be composed of more than 100 monosaccharides,
extend out from the core protein, and remain separated from each
other because of charge repulsion.
• The resulting structure resembles a “bottle brush” (Figure 14.5). In
cartilage proteo -glycan, the species of glycosaminoglycan's include
chondroitin sulfate and keratan sulfate.

30. Linkage between the carbohydrate chain and the
protein
• This linkage is most commonly through a trihexoside
(galactose-galactose-xylose) and a serine residue,
respectively. An O-glycosidic bond is formed between
the xylose and the hydroxyl group of the Serine.

31. Proteoglycan aggregates:
• The proteoglycan monomers associate with a molecule of hyaluronic
acid to form proteoglycan aggregates. The association is not covalent,
but occurs primarily through ionic interactions between the core
protein and the hyaluronic acid. The association is stabilized by
additional small proteins called link proteins.
• Main component of cartilage Provide strength and resilience
• 30 proteoglycans present on cell surface by transmembrane proteins
or attach lipid fraction of lipids.

33. • Fibronectin
• A protein in extracellular meshwork can bind fibrin,
collagen, and heparin sulphate called integrin have
too much binding sites for macromolecules.
• Proteoglycan can form aggregates of enormous size
that can bind to hyaluronic acid. Protein core namely
aggrecan present in these aggregates interact
strongly with collagen in extra cellular matrix of
cartilage and contribute in tensile strength of
cartilage.

34. functions
• As a constituent of extracellular matrix or ground substance: Interacts
with collagen and elastin
• Acts as polyanions: GAGS present in proteoglycans are polyanions and
hence bind to polycations and cations such as Na and K. Thus attracts
water by osmotic pressure into extracellular matrix contributing to its
turgor
• Acts as a barrier in tissue: Hyaluronic acid in tissues acts as a cementing
substance and contributes to tissue barrier which permit metabolites to
pass through but resist penetration by bacteria and other infective
agents.
• Acts as lubricant in joints: Hyaluronic acid in joints acts as a lubricant and
shock absorbant. Intra articular injection of hyaluronic acid in knee joints is
used to alleviate pain in chronic osteoarthritis of knee joints

35. Glycoproteins
• Oligosaccharides
• 1-70 % varies carbohydrates
• Complex, information rich material
• Most of secreted proteins include blood proteins
• Immunoglobulins, hormones ( FSH, LH, TSH)
• Lactalbumin, egg white, bone and cartilage
• Ceruloplasmin (iron and copper containing protein)
• Cell surface recognition (with other cells, virus and bacteria)
• Cell surface antigenicity (ABO)
• Extra cellular matrix (support and structure)
• Mucin (protective lubricant)

36. Glycolipids
• Mucilage
• Resemble glue and adhesive proprty like protein, starch, gum
• Which do not diffuse through most of membranes
• Agar (H2so4 with galactose)
• Agar form solution in hot water which set on cooling
• Non digestible used as laxative
• Medium for bacterial growth
• Vegetable gum (pentose or hexose or both )
• Gum Arabic on hydrolysis yield galactose, arabinose, Glucuronic acid
• Used in preparation of pharmaceutical adhesive.