Proteoglycans: Biological Roles and Strategies
(A)
C
C/AC
CHzOH 0
COOH 0
HO~'\ -
O~O~ '\
Jill
H
OH
COCH ,
- - 4GlcAfJI-- 3GlcNAcpl-/
hondroitinases
AC/ABC,
hyaluronidase
streptomyces
il4,5_uronic acid-GlcNAc
(unsaturated disaccharide)
GlcNAc-GlcA-GlcNAc-GlcA
(saturated tetrasaccharide)
(B)
--4GlcNAc 1ft--- 3GallP-345
Fig. 24.3. Structure of hyaluronan, cleavage by chondroitinases and hyaluronidases and degradation
products (A) and structure of the repeating disaccharide unit of keratan sulfate (B). GlcNAc in KS
replaces the position of uronic acid and Gal that of hexosamine in HA and GaIAGs. Alternating glycosidic bounds (31.--;.3 and (31.--;.4 are then the same with HA and GalAGs
Chondroitin sulfate differs from HA in two major structural features:
(1) GlcNAc of HA is replaced with GalNAc, i.e., the structure of the repeating
unit is [--3>4GlcABl--3>3GalNAcBl--3>] (Fig. 24.4A) and
(2) CS is normally sulfated at C-4 or C-6 positions of GalNAc forming a sulfated
backbone. Furthermore, anyone of the available hydroxyl groups may be sulfated. Thus, except nonsulfated disaccharide units, mono- and disulfated or
even trisulfated may also be present, and the potential variations in terms of
longer sequences are numerous (Karamanos et al. 1994). CS is synthesized on
the characteristic linkage region oligosaccharide (-O-Xyl-Gal-Gal-GlcA) via
an O-glycosidic linkage to serine or threonine residues (Fig. 24.2). Chain
(A)
C
C/AC
CHzOH 0
COOH 0
HO~'\ -
O~O~ '\
Jill
H
OH
COCH ,
- - 4GlcAfJI-- 3GlcNAcpl-/
hondroitinases
AC/ABC,
hyaluronidase
streptomyces
il4,5_uronic acid-GlcNAc
(unsaturated disaccharide)
GlcNAc-GlcA-GlcNAc-GlcA
(saturated tetrasaccharide)
(B)
--4GlcNAc 1ft--- 3GallP-345
Fig. 24.3. Structure of hyaluronan, cleavage by chondroitinases and hyaluronidases and degradation
products (A) and structure of the repeating disaccharide unit of keratan sulfate (B). GlcNAc in KS
replaces the position of uronic acid and Gal that of hexosamine in HA and GaIAGs. Alternating glycosidic bounds (31.--;.3 and (31.--;.4 are then the same with HA and GalAGs
Chondroitin sulfate differs from HA in two major structural features:
(1) GlcNAc of HA is replaced with GalNAc, i.e., the structure of the repeating
unit is [--3>4GlcABl--3>3GalNAcBl--3>] (Fig. 24.4A) and
(2) CS is normally sulfated at C-4 or C-6 positions of GalNAc forming a sulfated
backbone. Furthermore, anyone of the available hydroxyl groups may be sulfated. Thus, except nonsulfated disaccharide units, mono- and disulfated or
even trisulfated may also be present, and the potential variations in terms of
longer sequences are numerous (Karamanos et al. 1994). CS is synthesized on
the characteristic linkage region oligosaccharide (-O-Xyl-Gal-Gal-GlcA) via
an O-glycosidic linkage to serine or threonine residues (Fig. 24.2). Chain