The mechanism of initiation of chondroitin sulphate synthesis by beta-D-galactosides.

M Bradbeer, J A Robinson, H C Robinson

Index: Biochem. Int. 21(6) , 1161-8, (1990)

Full Text: HTML

Abstract

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-Gal-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.