POLYPEPTIDES 77 



Yeast extract first separated d-alanine, pancreatic extract first separated 

 glycine. Yeast extract hydrolysed 



l-leucyl-glycyl-glycyl-glycine 



+ 85-9 



in such a way that the rotation fell, 1-leucine being split off. In the 

 hydrolysis of these polypeptides by the various enzymes we notice that 

 yeast always separates the amino acid at the beginning of the chain. 

 Though this occurs with most of the enzymes, yet differences in the 

 point of attack are noticeable : 



Point of attack by Point of attack by 



It seems, therefore, that we possess a sharp means of differentiating 

 between the various proteoclastic enzymes, but no certainty can as yet 

 be placed upon the method as the variations are too few. 



///. Changes in Serum under Different Conditions. 



Neither the blood plasma of the horse, ox or dog hydrolyses 

 glycyl-1-tyrosine, but this compound is hydrolysed by the blood plasma 

 of the rabbit and guinea pig. Abderhalden and Rona extended these 

 observations to human blood plasma in cases of disease : in some 

 diseases no hydrolysis occurred, in other diseases there was distinct 

 hydrolysis. 



The production of anaphylactic shock by the injection of protein 

 into the blood stream of animals has led Abderhalden and various 

 co-workers to ascertain whether the content of the blood plasma in 

 enzymes was influenced by injection. 



Egg-white and horse serum were injected into dogs and also 

 rabbits ; subsequent examination of the plasma showed that pro- 

 teoclastic enzymes were produced ; they were easily detected in the 

 dog's plasma by the hydrolysis of glycyl-1-tyrosine ; the rabbit's blood 

 plasma hydrolysed the compound more rapidly. 



Injection of silk-peptone, gelatin, caseinogen and other proteins 

 also caused the appearance of proteoclastic enzymes capable of hydro- 



