Occurrence of Metabolic Processes in Simple Proteins 



277 



Because a prolonged investigation, performed in many stages, of forms of 

 life from the complicated to the simple could not lead to the definition of the 

 actual Umiting level, below which the process of protein anabolism did not 

 occur, it may be thought that the correct way to approach the elucidation of this 

 problem would be to investigate it from the opposite direction, beginning with 

 the simple and going on to the complicated. 



We therefore tried to discover whether there occurred in simple proteins such 

 chemical processes as could develop into biological phenomena, i.e. could lead 

 to self-reproduction, the alteration of protein molecules and further development. 



From this point of view we had to investigate the possibility that processes 

 of formation and decomposition might occur in simple proteins, as well as the 

 extent to which the variability of the composition of proteins is governed by 

 alterations in the surrounding mediimi. 



We have shown in pubhshed work [i] that, as regards various labelled amino 

 acids and the peptide glutathione, 15 différent proteins have the power to in- 

 corporate the structural units of proteins into themselves at a rate which is of 

 the same order as that for complicated biological systems. 



This phenomenon has also been observed by other workers, the total number 

 of proteins investigated being as great as 22 and the number of labelled structural 

 imits more than 10. 



By means of a series of experiments it was shown that when free amino acids 

 and peptides are incorporated into proteins, there are formed peptide, disulphide 

 and other bonds characteristic of the protein molecule between the components 

 of the protein and the structural tmits being incorporated (Table i). 



Furthermore it has been shown by partial hydrolysis that the strength of the 

 bonds is substantially the same when tyrosine [i] or glycine are incorporated in 

 myosin whether the incorporation occurs in vivo or in vitro (see Fig. i). 



Fig. I. Alterations in residual nitrogen and radioactivity during the hydrolysis of 

 myosin labelled in vitro and in vivo. 



1. Residual nitrogen 



2. Radioactivity of protein labelled in vitro — acid hydrolysis 



3. „ „ „ „ in vivo— „ „ 



4. „ „ „ 5, in vitro — alkaline hydrolysis 



5. „ „ „ „ in vivo — „ „ 



