ENZYMES AS SYNTHETIC AGENTS 487 



can be estimated. Dakin and Dudley have found glyoxalase in 

 yeast, an organism which is capable of solving its synthetic 

 problems upon a diet containing glucose and ammonium com- 

 pounds as the sources of its carbon and nitrogen respectively. 

 If subsequent work should show the enzyme to be widely 

 distributed in the plant kingdom, it will have to be seriously 

 considered as a possible aid in the production of amino-acids, 

 and as one link in the chain relating carbohydrate metabolism 

 to protein synthesis. 



3. The Hydrolysis of Protein Reserves 



Logically the next step would seem to be to consider the 

 part played by enzymes in the subsequent construction of pro- 

 teins from the primary amino-acids. Unfortunately this field is 

 almost untouched, and it is impossible to attack it directly. In 

 this section the present position of our knowledge of the hydro- 

 lysis of the storage proteins of the plant will be first discussed. 

 This will be'followed in the subsequent section by a considera- 

 tion of the attempts that have been made to produce reversible 

 catalysis in the hydrolyses of proteins by altering concentration 

 conditions. 



At the present time, when the decomposition products of the 

 hydrolysis of proteins are still incompletely known, and when 

 the series of hydrolytic changes accompanying that hydrolysis 

 cannot be pictured, it is natural that there should be con- 

 siderable confusion in the definition of the proteinases, the 

 enzymes or groups of enzymes which are responsible for the 

 hydrolysis. 



In the animal kingdom the simplest classification is based 

 upon the distribution of the enzymes within the body, and by 

 this means it is possible to distinguish three groups of pro- 

 teinases, viz. the peptase (pepsin) of the gastric secretion, the 

 tryptase (trypsin) of the pancreas, and the ereptase (erepsin) of 

 the intestinal mucus. 1 



In addition to this difference in origin, the peptases are 

 usually credited with an activity, restricted to slightly acid 

 solutions, which does not produce complete hydrolysis of the 

 protein digested, the products formed being albumose and 

 peptones. 



1 For a general account, see Euler, General Chemistry of Enzymes^ translated 

 by Pope, pp. 33 et seq, 



32 



