The proteinpolysaccharides of bovine nucleus pulposus.

Bovine nucleus pulposus has been found to be a good source of a series of proteinpolysaccharides containing chondroitin 6-sulfate and keratan sulfate. Six distinct fractions have been separated, totaling 40 % of the dry weight of the tissue. Each fraction contains protein, chondroitin B-sulfate, and keratan sulfate, but the proportions of these components are different in each fraction. Of these six fractions, the one called PPL3 is obtained in largest yield (17%), has the lowest content of protein (14%) and the highest content of chondroitin sulfate (45%), and also contains keratan sulfate (35%). On sedimentation velocity studies in the analytical ultracentrifuge under a wide range of conditions, it appears to be homogeneous. Sedimentation equilibrium studies at low initial concentrations indicate some degree of polydispersity and a weight average molecular weight of 171,000. On zone electrophoresis the chondroitin sulfate, keratan sulfate, and protein move together. Fraction PPW has almost the same amino acid profile as the corresponding fraction from bovine nasal cartilage, although these fractions differ greatly in protein and keratan sulfate contents. The data provide reasons to believe that chondroitin sulfate and keratan sulfate are parts of the same molecule. Three other fractions, called PPL4, PPL5, and PPL6, show a regular increase in sedimentation velocity, a regular decrease in speed of migration on zone electrophoresis, a regular increase in protein content, and a ratio of chondroitin sulfate to keratan sulfate which is constant (0.62) and differs from that of PPL3 (1.3). For each of these fractions, on zone electrophoresis, protein, chondroitin sulfate, and keratan sulfate stand or move together. There is no evidence that in this tissue any independent kinetic component exists which contains only chondroitin sulfate or only keratan sulfate.