Struktur und Stoffwechsel von Glykosaminoglykan-Proteinen, I. Die Keratansulfat-Peptide der Rinder-Cornea

Abstract

The glycosaminoglycan-peptides of bovine cornea were separated analytically by combined Ecteola and CPC chromatography. After proteolysis with papain, the content of chondroitin was about 3%, chondroitin-4-sulphate 34-43%, and keratan sulphate 54-63%. The keratan sulphate and the chondroitin-4-sulphate of the cornea were separated into various sub-fractions. Four keratan sulphate-peptides were prepared, which were free from chondroitin-4-sulphate and were homogenous in the ultracentrifuge and in electrophoresis. The sulphate content of each fraction increased and corresponded, in fraction IV, to 20% excess sulphate. While the ratio galactose/glucosamine remained constant at 1 for all the fractions, the amino acid content of the keratan sulphate-peptide complexes decreased to about one half from the first t the fourth fraction. The molecular weight, however, increased from fraction I to IV from 8600 to 19800. Aspartic acid was the dominant amino acid at about 30% in all four fractions. Incorporation experiments with S35O4 in vitro gave a direct demonstration of a keratansulphotransferase in the cornea. The specific radioactivity of all the keratansulphate fractions was constant and independent of the molecular weight and sulphate content.