THERMODYNAMICS 451 



the right which results from the introduction of a proteolytic 

 enzyme into the system must result in a corresponding shift in the 

 equilibrium of the system anhydrous enzyme + hydrated enzyme 

 towards the left and vice versa. Since the enzyme is usually 

 present in small concentrations compared with the protein, the 

 shift in the equilibrium between the two forms of the enzyme must 

 be large compared with that of the equilibrium between the protein 

 and its products; or else the energy expended in a shift of the enzyme- 

 equilibrium must be great compared with the energy expended in a 

 shift of the protein equilibrium. The latter appears to be the more 

 probable view; since, otherwise, the shift in the protein-equilibrium 

 would probably be in all cases too small to be observed, and, 

 moreover, we know that the reaction of protein hydrolysis is 

 only very faintly exothermic (65) (23) (25) (40) so that the energy 

 change involved in a shift in the equilibrium between protein and 

 the products of its hydrolysis is probably very small, and a slight 

 shift in the equilibrium of a relatively very small amount of enzyme 

 might suffice, if the reaction of enzyme hydration involved a 

 relatively considerable energy-change, to provide the energy for a 

 considerable change in the equilibrium of a relatively large mass of 

 protein. 



It will be observed, therefore, that the processes of the enzymatic 

 hydrolysis and synthesis of proteins do not necessarily involve 

 any deviation from the laws of thermodynamics, in spite of the 

 fact that the enzyme which catalyses these processes markedly in- 

 fluences the equilibrium between the protein and its products. In 

 the analogous case which is afforded by the enzymatic synthesis 

 and hydrolysis of fats Dietz (14) assumes that because the station 

 of equilibrium is altered by the presence of the enzyme the second 

 law of thermodynamics must be violated in these systems, for, he 

 argues, since the catalysor (enzyme) can be withdrawn from the 

 system without the expenditure of any work, it would only be 

 necessary to allow the system to come to equilibrium in the pres- 

 ence of the enzyme and then withdraw the enzyme and allow it to 

 come to its normal station of equilibrium and then reintroduce the 

 enzyme, and so forth, to bring about an endless cycle of changes 

 and to secure an unlimited quantity of energy without the expendi- 

 ture of any work. But in this argument, it should be pointed out, 

 Dietz assumes the answer to the very question at issue; he assumes 

 in a word, that the enzyme in question is a "typical" catalysor, 



