ENZYMES. 59 



A. DANILEWSKI first made the observation that concentrated solutions 

 of peptic cleavage products of protein substances separates an insol- 

 uble substance under the influence of rennin. This phenomenon has 

 since been observed by various investigators and the precipitate has 

 been called plastein by SAWJALOW l and coagulose by LAWROW. 2 The same 

 phenomenon is also obtained by other proteolytic enzymes. 3 The plas- 

 teins are considered by various investigators as synthetically formed 

 protein. The best proof for this view has been given by HENRIQUES 

 and GJALBACK. They show with the formol titration (see Chapter II) 

 that the nitrogen titratable by formol diminishes in the reaction and 

 they also found that the nitrogen precipitatable by tannic acid was 

 increased in the plastein formation. In a later work these authors 

 find that peptic cleavage products from proteins show a plastein for- 

 mation when under the influence of pepsin-hydrochloric acid in con- 

 centrated solution while in dilute solution the cleavage goes further and 

 they conclude from this that the process is reversible. Even protein 

 which has been partly split by acid or alkali shows a plastein formation 

 with pepsin-hydrochloric acid. 4 



The behavior of amygdalin and its cleavage products with enzymes 

 requires special mention. The cleavage takes place step by step as 

 follows : 



. (1) 



Amygdalin Mandelic acid nitrileglucoaide Glucose 



. (2) 



Mandelic acid nitrileglucoside Mandelic acid nitrile Glucose 



..... (3) 



Mandelic acid nitrile Benzaldehyde Hydrocyanic acid 



The entire process with the formation of the end products sugar, 

 benzaldehyde and hydrocyanic acid takes place under the influence of 

 emulsin from almonds. The first part of the process can be especially 

 brought about by the influence of yeast (FISCHER) 5 and the second and 

 third parts under the influence of prunase from the leaves of Pruneae. 6 Of 



iZeitschr. f. physiol. Chem., 54, 119 (1907). 



*Ibid., 61, 1; 53, 1 (1907); 56, 343 (1908); 60, 520 (1909). v 



3 Kurajeff, Hofmeister's Beitrage, 4, 476 (1904); Niirnberg, ibid., 4, 543 (1904). 



4 Zeitschr. f. physiol. Chem., 71, 485 (1911); 81, 439 (1912). 



5 Ber. d. d. chem. Gesellsch., 28, 1508 (1896). 



H. E. Armstrong, E. F. Armstrong and Horton, Proc. Roy. Soc., 85, 359, 363, 

 370 (1912). 



