CHEMICAL MECHANICS OF SYNTHESIS 439 



the protein, casein, from which paranuclein is derived and of 

 which it forms a large and integral proportion. The plasteins, 

 on the other hand, would appear to form, antigenically speaking, 

 a group of substances which are very closely related to one 

 another and probably contain a large common fraction. 



3. The Chemical Mechanics of the Fermentative Synthesis 

 of Proteins. We have seen in section 1 that in instances of 

 "typical" catalytic hydrolysis, although the degree of hydrolysis 

 in dilute systems, under the influence of a catalysor, may be prac- 

 tically complete, yet, if the solution of the products be concen- 

 trated, the station of equilibrium will be shifted and may be 

 shifted to such an extent that the pure products are not in 

 equilibrium and an appreciable quantity of substrate may be re- 

 stored to the system under the influence of a catalysor. Hence 

 it was natural to suppose, as Taylor did (loc. cit.) that the synthe- 

 sis of protamin, accomplished through the action of trypsin upon 

 the concentrated products of its hydrolysis, is an example of the 

 reversion of a " typical" catalysed reaction in which the catalysor 

 plays no part in determining the final equilibrium. Neverthe- 

 less it must be recollected that the validity of this view can by 

 no means be regarded as proven until it has been shown that the 

 station of equilibrium in the presence of the catalysor is definitely 

 the same as it is in its absence, and this has not been done; 

 indeed, the great technical difficulty of the problem, as it at 

 present appears to us, discourages the attempt. Moreover, 

 there are many facts, a number of which have been alluded to 

 in the previous chapter, which speak very decidedly against the 

 view that the fermentative syntheses of proteins are instances 

 of " typical" catalytic reversion. To those which have already 

 been dwelt upon may be added the following. 



We have seen that the velocity of protein hydrolysis is, under 

 certain conditions, directly proportional to the concentration of 

 the ferment, under others proportional to the square root of the 

 ferment-concentration (Chap. XVI, section 3). If the proteolytic 

 ferments act as " typical" catalysors and do not in any way affect 

 the final equilibrium in the system, then the velocity of synthesis 

 must also vary directly or as the square root of the ferment- 

 concentration, for otherwise the ratio between the velocity con- 

 stants of the forward and opposed reactions would be a function 

 of the ferment-concentration and, since the station of equilibrium 



