68 PHYSICAL CHEMISTRY IN BIOLOGY. 



certain cases this retardation can be explained by a reverse reaction (syn- 

 thesis) (page 59), in others no reverse reaction can be detected. That 

 the inversion of cane-sugar is retarded by invert sugar has been claimed 

 by many (HENRI/ A. J. BnowN, 2 BARENDRECHT, S ARMSTRONG 4 ), and 

 indeed BARENDRECHT claims that dextrose as well as levulose 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. ARM- 

 STRONG 5 found that invertin, maltase and lactase are retarded by just 

 those varieties of sugar which are produced by their activity. 



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

 7-tyrosine by yeast-press juice has recently been studied by ABDER- 

 HALDEN and GiGON. 6 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 67). 



There also exist proteins which act retardingly upon the digestion 

 of other proteins. The tryptic digestion of easily split protein bodies 

 is retarded by the difficultly digested white of egg (DELEZENNE and 

 PozERSKi, 7 VERNON, S GOMPEL and HENRI, 9 HEDiN. 10 The white of 

 egg takes up a part of the enzyme and makes this partly inactive. At 

 this time we must also mention the retarding action which the proteo- 

 lytic primary cleavage products (proteoses, peptones) exert upon diges- 

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

 with the products and in this way prevented from dissolving new pro- 

 tein (HEDIN 10 ). 



It has been known for a long time that blood-serum is able to retard 

 various enzymotic processes. Certain enzymes have their action retarded 

 even by normal serum. According to HAMMARSTEN and RODEN n normal 

 horse-serum retards the coagulation of milk, and the antitryptic action 

 of serum has been shown by several investigators (HAHN, 12 CAMUS and 



1 Zeitschr. f. physik. Chem., 39, 194, 1901. 



2 Journ. Chem. Soc., 81, 382, 1902. 



3 Zeitschr. f. physik. Chem., 49, 456, 1904. 



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



5 Ibid., 79, 360, 1907. 



6 Zeitschr. f . physiol. Chem., 53, 251, 1907. 



7 Compt. rend. soc. biol., 55, 935, 1903. 



8 Journ. of Physiol., 31, 495, 1904. 



9 Compt. rend. soc. biol., 58, 457, 1906. 



10 Zeitschr. f. physiol. Chem., 52, 422, 1907. 



11 Upsala lakare forenigs forh., 22, 546, 1887. 



12 Ber. klin. Wochenschr., 34, 499, 1897. 



