OLIGOSACCHARIDES DERIVED BY KERATANASE-II DIGESTION OF BOVINE ARTICULAR-CARTILAGE KERATAN SULFATES

Alkaline borohydride-reduced keratan sulphate chains from bovine articular cartilage (6-8-year-old animals) were subjected to a limit digest with the enzyme keratanase II. Using H-1-NMR spectroscopy, 25 reduced oligosaccharides deriving from keratan sulphate were shown to have the following structures [GlcNAc(6S)-ol represents N-acetylglucosaminitol 6-O-sulphate]: Gal beta(1-4)-GlcNAc(6S)-ol, Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)-ol, Gal(6S)beta(1-4)GlcNAc(6S)-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)-ol, Gal beta(1-4)GlcNAc(6S)beta(1-3)Ga1(6S)beta(1-4)GlcNAc(6S)-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-3)Gal(6S)(1-4) GlcNAc(6S)-ol, Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(6S)-ol, Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(6S)beta(1-3)Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(6S)-ol, Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(6S)-ol, Gal beta(1-4)(Fuc alpha(1-3)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)-ol, Gal(6S)beta(1-4)GlcNAc-(6S)beta(1-3)Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(GS)-ol, Gal beta(1-4)(Fuc alpha(1-3))GlcNAc(6S)beta(1-3)Gal(6S)(1-4)GlcNAc(6S)-ol, Gal beta(1-4)GlcNAc(6S)beta(1-6)(Gal beta(1-3))GalNAc-ol, Gal beta(1-4)GlcNAc(6S)beta(1-6)(NeuAc(2-3)Gal beta(1-3))GalNAc-ol, Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)beta(1-6)(Gal beta(1-3))GalNAc-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-6)(Gal beta(1-3))GalNAc-ol, Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)beta(1-6)(NeuAc(2-3)Gal beta(1-3))GalNAc-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-6)(NeuAc alpha(2-3)Gal beta(1-3))GalNAc-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-6)(NeuAc alpha(2-3)Gal beta(1-3)GalNAc-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)beta(1-6)(Gal beta(1-3)GalNAc-ol, Gal(6S)beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)beta(1-6)(NeuAc alpha(2-3)Gal beta(1-3))GalNAc-ol, NeuAc alpha(2-6)Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)-ol, NeuAc alpha(2-3)Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal beta(1-4)GlcNAc(6S)-ol, NeuAc alpha(2-6)Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal(6S)beta(1-4)GlcNAc(6S)-ol, NeuAc alpha(2-3)Gal beta(1-4)GlcNAc(6S)beta(1-3)Gal(6S)beta(1-4)GlcNAc(6S)-ol and NeuAc alpha(2-3)Gal(6S)beta(1-4)GlcNAc(6S)beta(1-3)Gal(6S beta)(1-4)GlcNAc(6S)-ol. Proton chemical shifts for these oligosaccharides were assigned using one- and two-dimensional NMR spectroscopic methods. These results confirm the findings of Nakazawa et al. [Nakazawa, K., Ito, M., Yamagata, T. and Suzuki, S. (1989) in Keratan sulphate: chemistry, biology and chemical pathology (Greiling, H. and Scott, J. E., eds) pp. 99-110, The Biochemical Society, London], namely that keratanase II cleaves the O-glycosidic bond of a beta(1-3)-linked 6-O-sulphated N-acetylglucosamine. However, the internal sulphated N-acetylglucosamine in the sialylated capping oligosaccharides is not cleaved because of the proximity of the sialic acid residue. In addition, keratanase II is the only degradative method examined so far which can cleave the glycosidic bond of a fucosylated N-acetylglucosamine residue as fucose residues confer resistance to both keratanase and hydrazinolysis/nitrous acid fragmentation.