126
P. W. KENT
(194-197)
keratosulfate, hyaluronic acid (198), heparin and heparitin
sulfates (195).
In all these cases, D-glucosamine or D-galactosamine occurs, the acidic
properties arising partly from ester-sulfate groups and partly from
uronic acids. Chondroitin sulfate A, found predominantly in costal and
tracheal cartilage, nasal septa, aorta, and bone, consists of a repeating
disaccharide in which D-glucuronic acid is linked through the
3)
positions to N-acetyl D-galactosamine. The ester sulfate is believed to be
located at C-4 of each amino sugar residue (Fig. 15).
FIG. 15. Chondroitin sulfate A.
Chondroitin sulfate C, found in skin, heart valves, bone, and tendon,
like A is an unbranched structure. In this case (Fig. 16), the sulfate ester
groups are located at C-6 of the amino sugar residues. Both A and C are
FIG. 16. Chondroitin sulfate C.
hydrolyzed by testicular hyaluronidase and in two respects differ from
derman sulfate (formerly chondroitin sulfate B), found particularly in
skin and aorta. This sulfated substance is comprised of N-acetyl-Dgalactosamine linked to L-iduronic acid, with sulfate esters located at
C-4 of the amino sugar residues (Fig. 17).
OH
NHAc
OH
FIG. 17. Derman sulfate (chondroitin sulfate B).
Keratosulfate of skin and cornea, on the other hand, is uronic acid
free and is comprised of D-galactose and N-acetyl-D-glucosamine, these
being linked alternately in ß-(l-> 4) and /?-(!-» 3) positions (Fig. 18)