Struktur und Stoffwechsel von Glykosaminoglykan-Proteinen, III. Die Chondroitin-Peptide der Rinder-Cornea

Abstract

Two chondroitin peptides, together with chondroitin 4-sulphate and keratan sulphate peptides were isolated from bovine cornea by combined chromatography on Ecteola cellulose and cellulose washed with cetyl pyridinium chloride. Chondroitin peptide I is practically free from sulphate (0.17%), while chondroitin peptide II contains 2.8% of sulphate. The predominant amino acids in chondroitin peptide I (total amino acid contept 48 /[mu]moles/100 mg) are aspartic acid, glutamic acid, and glycine. The amino acid composition of chondroitin peptide II (total amino acid content 15 /[mu]moles/100 mg) however, lies between that of chondroitin peptide I and chondroitin 4-sulphate peptide from bovine cornea. In the chondroitin peptides, threonine and serine are also partly destroyed by [beta]-elimination after treatment with alkali. Chondroitin peptide I is homogeneous in the analytical ultra-centrifuge, with a molecular weight of 16,700. The neutral sugars, xylose, galactose, and glucose were demonstrated in chondroitin peptide I by gas chromatography of their trimethylsilyl ethers. The chondroitin peptides from bovine cornea are split into unsaturated uronides by hyaluronate lyase; the rate of cleavage is lower than that of chemically desulphated chondroitin sulphate preparations, and much lower than that of hyaluronic acid.