F. Cheng et al., PATTERNS OF URONOSYL EPIMERIZATION AND 4- 6-O-SULFATION IN CHONDROITIN/DERMATAN SULFATE FROM DECORIN AND BIGLYCAN OF VARIOUS BOVINE-TISSUES/, Glycobiology, 4(5), 1994, pp. 685-696
Dermatan sulphate is a co-polymer of two types of disaccharide repeats
: D-glucuronate-N-acetylgalactosamine and L-iduronate-N-acetylgalactos
amine. The former can be O-sulphated at C-4 or C-6 of the galactosamin
e, whereas the latter contains almost exclusively 4-O-sulphated galact
osamine. A minor proportion of the L-iduronate may be O-sulphated at C
-2. Chondroitin sulphate has no L-iduronate- containing repeats. We ha
ve used our recently developed methods for sequence analysis of galact
osaminoglycans to investigate the structure of dermatan/chondroitin su
lphates of the proteoglycans decorin and biglycan derived from various
bovine tissues, like dermis, sclera, tendon, aorta, cartilage and bon
e. The glycan chains, radioiodinated at the reducing end, were partial
ly cleaved with specific enzymes (chondroitin lyases), and subjected t
o high-resolution polyacrylamide gel electrophoresis, blotting and aut
oradiography to identify fragments extending from the labelled reducin
g end to the point of cleavage. We used chondroitin B lyase to identif
y the location of L-iduronate, chondroitin AC-I lyase to locate D-gluc
uronate and chondroitin C lyase to cleave where D-glucuronate residues
were succeeded by 6-O-sulphated N-acetylgalactosamine. We could demon
strate tissue-specific, periodic and wave-like patterns of distributio
n for the two epimeric uronic acids, as well as specific patterns of s
ulphation in dermatan sulphates derived from either decorin or biglyca
n. For example, some dermatan sulphates contained n-glucuronate-rich d
omains that were always 6-sulphated (scleral decorin), others were alw
ays 4-sulphated (decorin from bovine dermis, cartilage and bone; bigly
can from aorta) or 6-sulphated near the linkage region, but 4-sulphate
d in more distal domains (decorin from porcine dermis and bovine tendo
n). Decorin from bone and articular cartilage, as well as biglycan fro
m articular and nasal cartilage, carried largely chondroitin sulphate
chains, but also some dermatan sulphate, whereas galactosaminoglycan c
hains derived from aggrecan of nasal cartilage were free of L-iduronat
e. Decorin and biglycan from the same tissue (articular cartilage or s
clera) had similar glycan chains. The two side chains in a biglycan mo
lecule are probably also similar to one another. The portion of the gl
ycan chains nearest to the core protein was substituted with charged g
roups to a variable degree, which may correlate with the structural fe
atures of the main chain.