Chemical Changes in Animal Organism. 297 



glycine will both yield a mixture of glycine and alanine 

 in equimolecular proportions. 



Various tissue extracts contain proteoclastic ferments 

 capable of hydrolyzing polypeptides, and it is obvious 

 that the investigations, of the action of the enzymes 

 obtained from these sources on the different polypeptides 

 will throw considerable light on the protein metabolism 

 of the organism. Numerous researches bearing on this 

 subject have been published in recent years. No rules 

 can yet be formulated as to the substances which are 

 attacked by given enzymes ; it will be observed, however, 

 that a very small difference even in the stereochemical 

 configuration will have an influence on the vulnerability 

 of substances. The specificity of action is, in fact, one of 

 the most striking characteristics of enzymes. 



It might be supposed, from the fact that the enzyme 

 appears in neither the initial nor final products of the 

 reaction, that a small amount will bring about the change 

 of an infinitively large amount of the substrate and 

 appear unchanged at the end. In practice this is not the 

 case, as usually the enzyme itself gets destroyed during 

 the course of the reaction. A large amount of work has 

 been carried out bearing on the chemical dynamics of 

 ferment action, which cannot be discussed in detail in 

 this place. One important point, however, which is of 

 considerable biological interest deserves a passing mention. 

 Certain hydrolytic processes are reversible, such as ester 

 formation (see p. 95), and it is of importance to ascertain 

 whether the reverse reaction can be brought about by the 

 ferment that is, whether synthesis as well as degradation 

 can be brought about. A limited number of instances of 

 synthesis by ferments has been discovered. When maltose 

 is treated with maltase it undergoes hydrolysis into two 

 molecules of glucose - 



