CHAPTER IX 



SPECIFIC POLYSACCHARIDE-SPLITTING 

 ENZYMES 



The decomposing action of bacterial enzymes on the soluble spe- 

 cific substance of pneumococci, with a description of the micro- 

 organisms, of the physical and biochemical properties of the en- 

 zymes and their effect on pneumococci in the test tube and in 

 experimentally infected animals. 



The discovery of the specific polysaccharides of Pneumococcus 

 was an incentive to a search for enzymes capable of decom- 

 posing these complex carbohydrates. During pneumococcal infec- 

 tions in man the soluble specific substance is present in the blood 

 and since it is excreted unchanged by the kidneys it was reason- 

 able to expect that none of the body tissues would be able to at- 

 tack this substance. No tissue has ever been found to possess the 

 power. Avery and Dubos 42 were the first to make a systematic hunt 

 for a ferment possessing the ability to digest the capsular poly- 

 saccharide of Pneumococcus. The authors tested enzymes from 

 animal and plant sources known to be active in the hydrolysis of 

 simpler carbohydrates, but all failed to affect the polysaccharides. 

 The similarity of these bacterial carbohydrates to hemi-cellulose 

 led the authors to search among the molds, yeasts, actinomyces, 

 and bacteria known to decompose substances allied to the cellu- 

 loses, but here again the quest was fruitless. 



FIRST ISOLATION OF POLYSACCHARIDE-SPLITTING ENZYME : SIII 

 BACILLUS 



Avery and Dubos reasoned that localities where large amounts 

 of organic materials — especially materials belonging to the group 

 of hemi-celluloses — accumulate and undergo decomposition were 

 most likely to harbor the desired organism. So they tried leaf mold, 



