The Action of Hydroxylamine on the Proteinpolysaccharides of Cartilage.

In the native state, the polysaccharides of cartilage act as if they were linked to protein by bonds labile to alkali such as ester bonds. This thought was more or less clearly expressed by Krukenberg (I), Schmiedeberg (2), and Levine (3) and was based on the ease of extraction of the polysaccharides from cartilage by alkali and on their resistance to extraction by water. Practically the entire content of chondroitin sulfate and keratin sulfate of bovine nasal cartilage is bound to protein as compounds called proteinpolysaccharides (PP). Under proper conditions a large part of these can be extracted with water as crude proteinpolysaccharide which can be sorted centrifugally into a fraction that sediments readily (PP-H), and one that does not (PP-L) (4). But the cartilage residue (CR) remaining after this extraction retains about a third of the total chondroitin sulfate that resists removal by water alone. Each of these three fractions into which whole cartilage can be separat#ed (CR, PP-H, and PP-L) contains chondroitin sulfate which can be released by treatment. wit.h 0.1 M NaOH (5). The released chondroitin sulfate in each case retains 5% peptides as well as hexose and sialate which resist removal by rather selective fractionation (5, 6). The present work had its inception in an examination of the stability of PP-Lr to NH,OH to see if evidence of ester links could be obtained. By this treatment the water-soluble PP-L appeared not to be degraded and yielded no product resembling chondroitin sulfate. In sharp contrast the waterinsoluble fractions PP-H and CR were both smoothly degraded, even at pH 7, and yielded pract,ically all of their chondroit.in sulfate in the form of a new proteinpolysaccharide easily soluble in water and similar to PP-L but having a lower protein content. The new proteinpolysaccharide was also formed by treatment of PP-H or CR with KCN at pH 9.