The mechanism of initiation of chondroitin sulphate synthesis by beta-D-galactosides
Bradbeer, M.; Robinson, J.A.; Robinson, H.C.
Biochemistry International 21(6): 1161-1168
1990
ISSN/ISBN: 0158-5231 PMID: 2127885 Document Number: 356828
Embryonic chicken cartilage was incubated in vitro with phenyl-.beta.-[6-3H]galactoside and cycloheximide. Free chondroitin sulphate chains initiated by galactoside were isolated and degraded to yield 3-O-.beta.-D-glucuronosyl D-galactose (GlcA-Gal) derived from the sequence, GlcA-Gal-GalGal-Xyl-Ser, which links the polysaccharide to protein. This enabled the distribution of 3H into specific galactose residues within the linkage oligosaccharide to be determined. Most of the 3H label (65%) was released as free galactose although 35% was recovered as GlcA-Gal. Similar experiments performed with unlabelled phenyl-.beta.-galactoside and [14C]galactose yielded 14C-labelled GlcA-Gal as a major product. We conclude that .beta.-galactosides initiate chondroitin sulphate synthesis primarily by serving as substrates for galactosyl transferase II.