82
1
General Principles
ranosyl uronic acid (α-L-iduronic acid). Some of the L-iduronic acids are sulfated at C-2.
Dermatan sulfate is found primarily in the skin [93].
7.4.4 Keratan Sulfate
Keratan sulfate consists of the disaccharide, N-acetyl-lactosamine, linked β-(1→3) to the
D-galactopyranose residue of the next N-acetyl-lactosamine unit. Keratan sulfate is the most
heterogeneous of the glycosaminoglycans, with variable sulfate content linked to C-4 or C-6
of the D-galactopyranose residue in lactosamine, and small amounts of L-fucose (6-deoxyL-galactose), D-mannose, and N-acetyl-neuraminic acid residues [93] (also see > Sects. 10.2
and > 14 on the occurrence of N-acetyl-D-neuraminic acid and L-fucose in other systems).
Keratan sulfate is found in the cornea, on the surfaces of erythrocytes, in cartilage, and in
bone.
7.4.5 Heparan Sulfate
Heparan sulfate consists of the repeating disaccharide β-D-glucopyranosyluronic acid-(1→4)N-sulfato-2-amino-2-deoxy-α-D-glucopyranosyl linked (1→4). This polysaccharide is linked
to a core protein to give a proteoglycan that is found as a matrix component of arterial wall,
lung, heart, liver, and skin [93].
8 Polysaccharides Containing Uronic Acids That Have Some
of Their Carboxyl Groups Inverted by a C-5 Epimerase
to Give New Polysaccharides with New Properties
8.1 Heparin Sulfate
Heparin sulfate is formed from heparan sulfate by the action of an enzyme, C-5 epimerase that
inverts the carboxylate group attached to C-5 of the D-glucopyranosyl uronic acid residues
to give the rare and unusual sugar, α-L-idopyranosyl uronic acid. Heparin sulfate is released
from the heparin of proteoglycans of mast cells into the blood stream when there is an injury
to blood vessels, in the heart, liver, lungs, and skin. The release of heparin near the site of the
injury acts as an anti-coagulating agent, preventing massive clotting of the blood and, hence,
preventing run-away clot formation [93].
8.2 Alginates
Alginates are found primarily in brown seaweeds in amounts of 18–40% by weight of the plant.
The majority is extracellular, being located between the cells [94]. One of the major species
of seaweeds that contains alginates is the giant kelp, Macrocyctis pyrifera. It grows along the
California coast of the US, the northwestern and southwestern coasts of South America, and
the southeastern coasts of Australia and New Zealand [95].
Alginates are formed from poly-D-mannopyranosyluronic acid by the action of a C-5
epimerase that inverts the C-5 carboxyl group to give approximately 33% (w/w) of the
1
General Principles
ranosyl uronic acid (α-L-iduronic acid). Some of the L-iduronic acids are sulfated at C-2.
Dermatan sulfate is found primarily in the skin [93].
7.4.4 Keratan Sulfate
Keratan sulfate consists of the disaccharide, N-acetyl-lactosamine, linked β-(1→3) to the
D-galactopyranose residue of the next N-acetyl-lactosamine unit. Keratan sulfate is the most
heterogeneous of the glycosaminoglycans, with variable sulfate content linked to C-4 or C-6
of the D-galactopyranose residue in lactosamine, and small amounts of L-fucose (6-deoxyL-galactose), D-mannose, and N-acetyl-neuraminic acid residues [93] (also see > Sects. 10.2
and > 14 on the occurrence of N-acetyl-D-neuraminic acid and L-fucose in other systems).
Keratan sulfate is found in the cornea, on the surfaces of erythrocytes, in cartilage, and in
bone.
7.4.5 Heparan Sulfate
Heparan sulfate consists of the repeating disaccharide β-D-glucopyranosyluronic acid-(1→4)N-sulfato-2-amino-2-deoxy-α-D-glucopyranosyl linked (1→4). This polysaccharide is linked
to a core protein to give a proteoglycan that is found as a matrix component of arterial wall,
lung, heart, liver, and skin [93].
8 Polysaccharides Containing Uronic Acids That Have Some
of Their Carboxyl Groups Inverted by a C-5 Epimerase
to Give New Polysaccharides with New Properties
8.1 Heparin Sulfate
Heparin sulfate is formed from heparan sulfate by the action of an enzyme, C-5 epimerase that
inverts the carboxylate group attached to C-5 of the D-glucopyranosyl uronic acid residues
to give the rare and unusual sugar, α-L-idopyranosyl uronic acid. Heparin sulfate is released
from the heparin of proteoglycans of mast cells into the blood stream when there is an injury
to blood vessels, in the heart, liver, lungs, and skin. The release of heparin near the site of the
injury acts as an anti-coagulating agent, preventing massive clotting of the blood and, hence,
preventing run-away clot formation [93].
8.2 Alginates
Alginates are found primarily in brown seaweeds in amounts of 18–40% by weight of the plant.
The majority is extracellular, being located between the cells [94]. One of the major species
of seaweeds that contains alginates is the giant kelp, Macrocyctis pyrifera. It grows along the
California coast of the US, the northwestern and southwestern coasts of South America, and
the southeastern coasts of Australia and New Zealand [95].
Alginates are formed from poly-D-mannopyranosyluronic acid by the action of a C-5
epimerase that inverts the C-5 carboxyl group to give approximately 33% (w/w) of the