384 



CHEMICAL DYNAMICS 



Euler has arrived at the conclusion that in solutions of glycyl- 

 glycin which contain a base, only the salt of the dipeptid under- 

 goes hydrolysis. In terms of recent theories of catalysis (18) 

 this may be held to indicate that the substance which actually 

 undergoes hydrolysis is the dipeptid ion. 



For high ferment-concentrations the velocity of the hydrolysis 

 of glycyl-glycin is, according to Euler, directly proportional to 

 the concentration of erepsin. If, however, the ferment concen- 

 tration is low, then the value of k, calculated from the mono- 

 molecular formula, increases much more rapidly than the con- 

 centration of erepsin. 



The influence of various added substances (salts, amino-acids, 

 and so forth) upon the rate of hydrolysis of dipeptids by liver- 

 extract has been studied by Abderhalden and Gigon (3). They 

 find that dilute solutions of KCN accelerate while strong solu- 

 tions greatly retard the hydrolysis of d-1-leucyl-glycin; sodium 

 fluoride strongly retards the hydrolysis of d-1-leucyl-glycin and 

 of glycyl-1-tyrosin; "physiological salt solution" has no effect 

 upon the rate of hydrolysis. In high concentrations both mag- 

 nesium chloride and sulphate depress the rate of hydrolysis; 

 calcium chloride accelerates the hydrolysis and strontium chlo- 

 ride is indifferent, the substrates being d-1-leucyl-leucin and glycyl- 

 1-tyrosin. 



The effect of amino-acids upon the rate of hydrolysis is of 

 surpassing interest since these are the products of the reaction, 

 and if they exert an influence upon the rate of hydrolysis they will 

 induce more or less marked deviations in the relation between 

 the duration and the extent of hydrolysis from that which would 

 be indicated by the monomolecular law or by Henri's modifi- 

 cation of the monomolecular law, described above. Employing 

 glycyl-1-tyrosin they find that : 



