Characteristics of chondroitin sulfate proteoglycans of differentiating nonchondrogenic tissues

The chondroitin 4- and 6-sulfate proteoglycan monomers from two differentiating tissues (brain and muscle of 14-day chick embryos) were compared by indirect means, including use of chondroitinase AC, with the major class of cartilage chondroitin sulfate proteoglycan monomers. In addition to slower sedimentation in sucrose density gradients, the monomers from both noncartilaginous tissues have longer chondroitin sulfate chains and exhibit little difference in the susceptibilities of their core proteins to papain and trypsin, in contrast to the cartilage monomer. However, slight differences in average sizes and polydispersity of fragments formed by enzyme treatments and beta-elimination were found between the proteochondroitin sulfate monomers of embryonic brain and muscle. Although the chondroitin sulfate chains are attached to separate tryptic peptides from the majority of other sulfated glycosaminoglycans in the noncartilaginous tissues, it is still uncertain whether these units form part of separate proteoglycan monomers.