Comparative biochemistry of keratosulfates.

Keratosulfate was first isolated from bovine cornea in 1953 by Meyer et al. (2) and its repeating unit structure determined to be (1 3 3)P-n-galactopyranosyl-(1 + 4)-2-acetamido-2-deoxy-Po-glucopyranosyl 6-sulfate (3). This compound was later reported present also in human cartilage (4) and in nucleus pulposus (5). u-Glucosamine was characterized as the hydrochloride and n-galactose as the or-methylphenylhydrazone upon isolation from preparations from human cartilage (4). Subsequently, a polymer of galactose and glucosamine, isolated from shark cartilage by Mathews (6) and Furuhashi (7), had a molar ratio of ester sulfate to hexosamine of 1.3 to 1.7 and appeared to be a polysulfated analogue of keratosulfate. n-Glucosamine and n-galactose were also isolated and characterized as derivatives (7). However, the preparations from cornea and from shark cartilage, upon closer examination, revealed other chemical differences, particularly in residual amino acids and in the presence of galactosamine in preparations from shark cartilage. For this reason, the homologous compounds in tissues of other vertebrates were examined. The results obtained indicate that cornea keratosulfate peptide and cartilage keratosulfate peptide are fragments of two different classes of connective tissue molecules. Recently, Meyer, Seno, Anderson, Lippman, and Hoffman (8) reported that chondroitin sulfate was linked to skeletal keratosulfate in contrast to our findings (1) that the galactosamine in vertebrate skeletal keratosulfate was not associated with glucuronate and that chondroitin sulfate was not a component of skeletal keratosulfate.