ENZYMES 185 



tween animal charcoal and trypsin, is primarily irreversible. The 

 trypsin is fixed, water is unable to tear the trypsin from the char- 

 coal though casein is able to do so (S. G. HEDIN). It is seen ; accord- 

 ingly, that trypsin undergoes a change on the surface of charcoal 

 similar to that undergone by dyes on fibers and if the process were 

 to occur in the organism as it does on charcoal, the trypsin would 

 be permanently withdrawn from the mixture. If, however, the sub- 

 strate is digested and crystalloid cleavage products result, e.g., in the 

 cleavage of fibrin by trypsin, the adsorption ceases of its own accord 

 and the enzyme becomes free for further use, acting like a true 

 catalyzer. 



This serves to explain the significance of the surfaces of the sub- 

 strate on enzyme action. The action increases in speed in accord- 

 ance with extent of surface per unit of weight. E. ABDERHALDEN 

 and PETTIBONE* demonstrated this in the digestion with pancreatic 

 juice of albumen coagulated in different ways. 



In the case of enzymes their electrochemical nature is more im- 

 portant than in the case of other colloids, and influences their ad- 

 sorption. 



We frequently observe that if the proper H or OH ion concentra- 

 tion is absent, an enzyme acts feebly on its substrate. Many neutral 

 salts favor enzyme action; others inhibit it. For instance, pepsin 

 acts strongly in acid solution only, trypsin in alkaline solution only. 



The investigations of L. MiCHAELis* 2 and his co-workers show 

 that the electric charge of different enzymes varies (see H. Iscov- 

 Esco* 3 ) and that, proportionately to the charge, they are unequally 

 adsorbed by various substrates. 



We have previously mentioned that electropositive gels or suspen- 

 sions, e.g., ferric oxid, completely adsorb electronegative solutions, 

 e.g., serum albumin. An electronegatively-charged mastic or kaolin 

 suspension completely attracts to itself serum albumin, only when it 

 has become electropositive by acidification. 



These investigations gave the following results for a group of 

 enzymes. In the table (see p. 186) X signifies a pronounced electric 

 migration (to cathode or anode), i.e., complete adsorption; signi- 

 fies no migration or no adsorption; X 0, X, respectively, 

 more or less migration or adsorption. 



