CHAPTER XVI 

 THE HYDROLYSIS OF THE PROTEINS 



1. The Proteolytic Enzymes as Catalysors. The fact that 

 proteins, in the presence of water, can be hydrolysed to ammo- 

 acids by prolonged heating, e.g., by superheated steam (126) 

 (80) (81) (76) (69) (70) (87) (115) without the addition to the 

 system of any acid, alkali or ferment, indicates that the process 

 of hydrolysis is occurring, although slowly, at all temperatures 

 and in the absence of catalysors other than, possibly, the hydrogen 

 or hydroxyl ions of water itself. The fact that, at ordinary 

 temperatures, catalysors can bring about the hydrolysis of pro- 

 teins shows that even at these temperatures the proteins are not 

 in equilibrium with their products. The influence of rising tem- 

 perature upon a chemical reaction is always twofold; it shifts 

 the station of equilibrium in one sense or in the opposite and, 

 always, it accelerates the reaction to a greater or less degree 

 (i.e., magnifies the velocity-constant). The action of heat upon 

 proteins must be in all cases to shift the station of equilibrium 

 in the direction of polymerization (i.e., condensation) since the 

 reaction of hydrolysis is faintly exothermic, but the fact that 

 fairly complete hydrolysis occurs at temperatures above 100 

 degrees shows that the shift in the equilibrium between the lower 

 protein complexes and the amino-acids which are the products of 

 their hydrolysis is not so great as to extinguish the reaction of 

 hydrolysis. The effect of high temperatures in accelerating the 

 auto-hydrolysis of proteins is to be looked upon, therefore, as 

 that of rendering readily detectable, through acceleration, a 

 reaction which occurs, although slowly, at all temperatures (133). 

 It is possible to demonstrate directly, however, and without 

 appeal to inference, that the hydrolysis of proteins in neutral 

 watery solutions does occur at normal temperatures; the velocity 

 of hydrolysis is, however, usually very low under these conditions. 

 Taylor has shown that an appreciable proportion of pure sterile 

 globulin kept in distilled water at ordinary temperatures for 

 18 months is hydrolysed to proteoses; he has also found that 



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