PROTEOLYTIC ENZYMES AS CATALYSORS 391 



The autohydrolysis of- the casdnates in neutral and faintly 

 alkaline solutions has been more extensively studied by E. H. 

 Walters (147) who has shown that the neutral caseinates of 

 lithium, sodium and potassium in sterile solution undergo com- 

 paratively rapid autohydrolysis, approximately five per cent of 

 the protein being hydrolysed in ninety-six hours at 37.5° C. 

 The "basic" caseinates (neutral to phenolphthalein) of the same 

 bases undergo autohydrolysis at a slightly higher velocity. The 

 velocity of the autohydrolysis of the ''basic" caseinates of cal- 

 cium and barium is about three times as great as that of the 

 autohydrolysis of the caseinates of lithium, sodium or potassium, 

 indicating very clearly that some factor other than the H+ or 

 OH' ions plays a part in determining the velocity of the 

 autohydrolysis. 



The proteolytic enzymes have long been regarded, by the 

 majority of investigators * as true catalysors; but the evidence 

 which has been brought forward in support of or in opposition 

 to this view has varied very much in character from time to 

 time. With the rapid gain in exact knowledge in the field of 

 physical chemistry which characterized the scientific advance 

 in the latter part of the last century, the characteristic features 

 of many catalytic processes became very thoroughly known and 

 certain catalytic reactions came to be regarded as "typical" 

 for no better reason than that they were the best studied and 

 therefore the best known. Now these so-called "typical" in- 

 stances of catalysis had in the first place attracted the attention 

 of investigators simply because of the marked peculiarities which 

 they exhibited and which appeared to differentiate them sharply 

 from other chemical reactions, and thus, by a not unnatural 

 process of circular reasoning these peculiarities came to be re- 

 garded as "typical" and diagnostic of "true" catalysis. Our 

 conceptions and definitions of "catalysis" have therefore altered 

 and enlarged as the number of "typical" instances has grown, 

 and, correspondingly, features in the mode of action of ferments 

 have been brought forward, at one time in support of the thesis 

 that the ferments are not true catalysors, and at another time 

 in support of the exact converse of this view. Unquestionably 

 attempts have been made by many authors to shape the phe- 

 nomena of fermentation into accord with prematurely rigid 

 * Starting with Berzelius and Liebig. Cf. Jacob Berzelius (8). 



