ENZYMES. 65 



which is. difficult to digest (DELEZENNE and POZERSKI/ 

 COMPEL and HENRI, 3 HEDiN 4 ). 



At this time we must also mention the retarding action which the 

 proteolytic primary cleavage products (proteoses, peptones) exert upon 

 digestion. These products are further split; a part of the enzyme is 

 combined with the products and in this way prevented from dissolv- 

 ing new protein (HEDIN) . 5 The retarding power of proteoses and pep- 

 tones upon rennin action is probably similar to the above. 6 



Finally, the end products of enzymotic activity i.e., bodies which 

 cannot be further split by the enzyme, have also a retarding action on 

 the enzyme action. That the inversion of cane-sugar is retarded by 

 invert sugar has been claimed by many (HENRI, 7 A. J. BROWN, S BAREN- 

 DRECHT, 9 ARMSTRONG 10 ), and indeed BARENDRECHT claims that glucose 

 as well as fructose has a retarding action, and that galactose has an 

 even stronger retarding action than the direct cleavage products of cane- 

 sugar. H. E. and E. F. ARMSTONNG U found that saccharase, maltase and 

 lactase are retarded by just those varieties of sugar which are produced 

 by their activity. The accumulation of the amylolytic cleavage prod- 

 ucts have according to SH. LEA, 12 a retarding action upon saliva. 



The retarding action of amino-acids upon the decomposition of glycyl- 

 Z-tyrosine by yeast-press juice has recently been studied by ABDERHALDEN 

 and GiGON. 13 They found that cleavage of peptides is retarded by 

 those optically active amino-acids which occur in the proteins. This 

 result is remarkable in consideration of the observations of FISCHER 

 and ABDERHALDEN that only those polypeptides were split by pancreatic 

 juice which are composed of natural optically active amino-acids (page 62). 



The retardation of the action of papain by egg protein and by serum, which 

 is prevented by heating or action of hydrochloric acid, as shown by the investiga- 

 tions of DELEZENNE, MOUTON and POZERSKI as well as by JONESCU and SACHS 14 

 is a peculiar behavior. 



. rend. soc. biol., 55, 935 (1603). 



2 Journ. of Physiol., 31, 495 (1904). 



3 Compt. rend. soc. biol., 58, 457 (1906). 



4 Zeitschr. f. physiol. Chem., 52, 422 (1907). 

 * Zeitschr. f. physiol. Chem., 52, 422 (1907). 



6 Ibid., 46, 307. 



7 Zeitschr. f . physik. Chem., 39, 194 (1901). 



8 Journ. Chem. Soc., 81, 382 (1902). 



9 Zeitschr. f. physik. Chem., 49, 456 (1904). 



10 Proc. Roy. Soc. (ser. B), 73, 516 (1904). 



11 Ibid., 79, 360 (1907). 



12 Journ. of Physiol., 1911. 



13 Zeitschr. f. physiol. Chem., 53, 251 (1907). 



14 Delezenne, Mouton and Pozerski, Compt. rend., 142; Jonescu, Bioch. Zeitschr., 

 2; Sachs, Zeitschr. f. physiol. Chem., 51, 488 (1907). 



