ENZYMES AS SYNTHETIC AGENTS 

 II. IN PROTEIN METABOLISM 1 



By J. H. PRIESTLEY, B.Sc, F.L.S. 



Professor of Botany, University of Leeds 



Much of the work upon the synthesis of carbohydrates has been 

 done with a view to solving the questions of constructive meta- 

 bolism in the plant, but in the study of protein metabolism 

 attention has been chiefly directed to the problems presented in 

 the animal organism. 



In the present paper, which is a survey of recent work, 

 the point of view taken will be the bearing that some of this 

 work upon proteins may possibly have upon constructive 

 metabolism in the plant. Considered from this standpoint, the 

 facts, so far as they are known to the present writer, may per- 

 haps be summarised without presenting too familiar an aspect. 



The problem of presentation is simplified in some respects 

 by the fact that, at the present time, questions of molecular 

 symmetry need scarcely be considered. They will emerge when 

 our knowledge of the various phases leading to the natural 

 proteins becomes much more detailed. 



In considering the possible significance of enzymes in the 

 construction of these complex bodies, it will be possible to draw 

 attention to only a few groups of problems out of a very wide 

 range. In plant physiology at the present time, the following- 

 questions seem to the writer worthy of attention in that they 

 may suggest opportunities for experimental attack through a 

 study of enzyme activity. 



i. The manner in which nitrogen is first included in the 

 simpler substances from which the protein is subsequently 

 formed. 



2. The possible relation of carbohydrate metabolism to the 

 synthesis of proteins. 



3. The role played by enzymes in the hydrolysis of storage 

 forms of proteins. 



4. The significance of recent attempts to produce a re- 

 versible reaction in definite cases of the hydrolysis of proteins 

 by enzymes. 



1 For Part I. see Science Progress, July 191 3. 



482 



