INHIBITION BY ALDOBIOURONATES IN PRECIPITATION OF PNEUMOCOCCAL TYPE-2 AND TYPE-3 SYSTEMS

Inhibitory effects were studied of the sodium salts of D-glucuronic acid, maltouronic acid, cellobiouronic acid, isomaltouronic acid, and gentiobiouronic acid on precipitation of antipneumococcal type II and type III sera by the homologous capsular polysaccharides. Earlier conclusions of Goebel, based on uronic acid-protein conjugates, were confirmed and extended. The results exclude a recently proposed structure of the type II polysaccharide with side chains of cellobiouronic acid, and are in accord with the original data obtained by methylation. The strong inhibition of the type II reaction by isomaltouronate indicates that the nonreducing end groups of D-glucuronic acid in the type II capsular polysaccharide are in the a anomeric form and are linked 1→6 to D-glucose. Isomaltose did not inhibit. Cellobiouronate was the best inhibitor of the type III reaction, in accord with the structure of the type III polysaccharide as a polycellobiouronic acid. © 1969, American Chemical Society. All rights reserved.