THE STRUCTURE OF THE KERATAN SULFATE CHAINS ATTACHED TO FIBROMODULIN ISOLATED FROM BOVINE TRACHEAL CARTILAGE - OLIGOSACCHARIDES GENERATED BY KERATANASE-II DIGESTION

The repeat region and chain caps of the N-linked keratan sulphates att ached to bovine tracheal cartilage fibromodulin were fragmented by dig estion with keratanase II, and the oligosaccharides generated were iso lated by strong anion-exchange chromatography. Each of these oligosacc harides has been examined by both HPAE chromatography and high field H -1-NMR spectroscopy. All of the capping oligosaccharides isolated term inated with alpha(2-3)-linked N-acetyl-neuraminic acid, and neither al pha(2-6)-linked N-acetyl-neuraminic acid chain terminators, nor fucose alpha(1-3)-linked to N-acetylglucosamine were found. The keratan sulp hate chains were short, with average lengths of five to seven disaccha rides, and the level of galactose sulphation varied along the length o f the chain. The repeat region and chain cap were confirmed as having the following general structure: [GRAPHICS] This study has identified a novel structure in fibromodulin, namely a cap containing a sulphated galactose adjacent to a non-reducing terminal N-acetyl-neuraminic aci d. We have also confirmed that the general structure of the repeat uni ts and chain caps of N-linked keratan sulphate attached to fibromoduli n isolated from bovine tracheal cartilage, is similar to that of O-lin ked keratan sulphate chains attached to aggrecan from non-articular ca rtilage. However, there are important differences in chain lengths and sulphation patterns.