"RACEMIZED" PROTEINS 31 



The objection, also raised by Kober, that racemized polypetids 

 are hydrolysable by trypsin is not valid because the reaction 

 depicted by Dakin is not, correctly speaking, racemization but 

 " enolization " and the structures of polypeptids formed from 

 racemic amino-acids and the so-called " racemized proteins" are 

 probably not in the least analogous. Finally, the fact, also 

 cited by Kober as an objection to Dakin's hypothesis, that not 

 all of the * amino-acids resulting from the complete hydrolysis 

 of enolized proteins are optically inactive, merely tends to show 

 that not all COHN groups are equally affected by alkali. 



According to Underbill and Hendrix (68) crude "racemized" 

 proteins produce toxic symptoms when introduced into the cir- 

 culation of animals. Purified "racemized" proteins exert no 

 toxic action. A portion, but not all of the toxic substance can 

 be removed from "racemized" proteins by extraction with alcohol. 

 Evidently the main reaction is complicated by the occurrence 

 of side-reactions chief among which must be hydrolysis which is 

 rather rapid in solutions of the alkalinity employed. 



In terms of the hypothesis of protein ionization outlined above 

 the "racemization" of proteins by alkali must consist in an ex- 

 change of hydrogen atoms in the enol group in accordance with 

 an equation such as: 



NH-CO- 

 I 

 R-CH-C(OH) = N-CH-RCOOH 



NH-CO- 

 I 

 R_C = C(OH)-NH-CH-R-COOH 



with consequent transformation of the double bond connecting 

 carbon and nitrogen in the COHN group into a single bond. 



LITERATURE CITED 



(1) Abderhalden, E., and Koelker, A. H., Zeit. f. physiol. Chem. 51 (1907), 



p. 294; 54 (1908), p. 363. 



(2) Abderhalden, E., and Van Slyke, D.D., Zeit. f . physiol. Chem. 74 (1911), 



p. 505. 



(3) Earth, L., Annalen der Chem. 152 (1869), p. 96. 



(4) Billitzer, J., Annalen der physik. 316 (1903), pp. 902 and 937. 



(5) Blasel, L., and Matula, J., Biochem. Zeit. 58 (1914), p. 417. 



(6) Bredig, G. Zeit. f. physik. Chem. 13 (1894), p. 191. 



(7) Broeck, Carl Ten, Journ. Biol. Chem. 17 (1914), p. 369. 



