POLYSACCHARIDE-SPLITTING ENZYMES 321 



pneumococcus a hexose, identified as glucose, and an aldobionic acid. 

 From the actual quantities of these two constituents found in the hy- 

 drolysate, and from the value of the acid equivalent of the polysaccha- 

 ride itself, it appears that this specific carbohydrate is built up from 

 glucose and glucuronic acid approximately in the ratio of 7 molecules of 

 hexose to 2 of uronic acid. The capsular carbohydrate of Type VIII 

 pneumococcus represents, therefore, an entity which is chemically dis- 

 tinct from the specific polysaccharide elaborated by the Type III pneu- 

 mococcus. 



That a chemical similarity between the two substances exists, how- 

 ever, may be seen from the results of the experimental work in which it 

 has been shown that the aldobionic acids appearing in the acid hydroly- 

 sates of both polysaccharides are identical. The proof of the identity of 

 these two uronic acids was made possible through the preparation of the 

 crystalline heptaacetyl methyl ester. Both derivatives show identical 

 crystalline structure, melting points, and specific rotations. Further- 

 more, a mixed melting point of the two derivatives shows no depres- 

 sion. Although the actual structure of the aldobionic acid is as yet un- 

 known, work is now in progress to establish this point. 



In view of the experimental evidence which has been presented, 

 showing that the aldobionic acids derived from the carbohydrates of 

 Types III and VIII pneumococcus are identical, it is believed that the 

 basis for the immunological crossing exhibited by these two specific 

 types of pneumococcus resides in the structural and configurational 

 identity of the uronic acid nucleus common to the encapsulating poly- 

 saccharides of both microorganisms. 



Sickles and Shaw 1283 reported that the enzyme from the new soil 

 bacillus was capable of destroying the purpura-producing action 

 of the VIII carbohydrate and of protecting mice against several 

 thousand minimal fatal doses of a virulent strain of Type VIII 

 Pneumococcus. Larger amounts of the enzyme failed to protect 

 mice against ten minimal fatal doses of Type III Pneumococcus. 

 The observations in these two papers describing the highly selec- 

 tive action of the enzyme on the soluble specific substance in con- 

 trast to the cross-agglutination present another pretty problem 

 for the chemo-immunologist. 



