THE SYNTHESIS OF THE PROTEINS 49 



juices. Since neither of these juices acted upon glycyl-1-tyrosine they 

 must be regarded as peptic in their nature. 



Abderhalden and Teruuchi used glycyl-1-tyrosine to determine the 

 nature of the enzymes in yeast juice, i.e. endotryptase, in papain and in 

 the juice of nepenthes. The two former hydrolysed it, and consequently 

 they contain tryptic enzymes ; the last had no action upon it, and the 

 enzyme of nepenthes is therefore like pepsin in its action. These 

 results confirm the observations of other investigators, and the confusion 

 concerning the nature of these enzymes would appear to be now settled 

 with certainty. 



The proteoclastic enzymes occurring in the germinating seeds of 

 wheat and the lupine appear, according to the results obtained by 

 Abderhalden and Schittenhelm, to have a stronger hydrolytic action 

 than trypsin, since they break up glycyl-glycine and dl-leucyl-glycine 

 which are unaffected by the enzyme of the pancreas. The same holds 

 good for the enzyme of the mushroom, although glycyl-1-tyrosine was 

 not hydrolysed ; this compound was apparently destroyed by other 

 enzymes in the mushroom. 



The enzymes of the various organs of the animal body have hydro- 

 lysed with few exceptions all the polypeptides upon which their effect 

 has been studied. Leucyl-leucine was not hydrolysed by the enzymes 

 of the liver of the ox, and in all probability this was due to the insolubility 

 of the polypeptide. The other striking result is that glycyl-1-tyrosine 

 was not hydrolysed by the enzymes of calf's brain, which attacked the 

 other polypeptides upon which it acted. The only diketopiperazine so 

 far investigated was glycine anhydride, and this was not converted into 

 glycine ; this result would point to the absence of anhydrides in the 

 products absorbed from the intestine. In general, the enzymes of the 

 organs are more powerful than trypsin and less selective in their action. 



The most interesting and astonishing facts were obtained by the 

 examination of the blood corpuscles, the plasma and serum. Red blood 

 corpuscles and platelets of the horse (but not of the ox) hydrolysed 

 glycyl-1-tyrosine, which was not attacked by white corpuscles obtained 

 from lymph or from pus cells, nor by the plasma or serum. Plasma 

 and serum both hydrolysed dl-alanyl-glycine, as also the tri- and tetra- 

 peptides diglycyl-glycine and triglycyl-glycine, which proves that the 

 enzymes in the plasma and serum are not trypsin (or erepsin) absorbed 

 from the intestine. Red blood corpuscles hydrolysed diglycyl-glycine, 

 and the splitting caused by the plasma and serum may be due to the 

 presence of the enzymes of the red blood corpuscles, either excreted 

 naturally, or produced during the separation of the constituents, which 

 PT. n. 4 



