114 CHEMISTRY OF THE PEOTEIDS CHAP, n 



naturally -occurring, active phenylalanin is converted almost com- 

 pletely into homogentisinic acid, while the racemosed phenylalanin 

 is only converted to the extent of 50 per cent. The four constitu- 

 tional formulae given below show that, because of the simultaneous 

 oxidation and reduction, changes take place not only in the side-chain 

 but also in the benzene ring. 



OH 







CH 2 CHNH 2 COOH CH 2 CHNH 2 COOH 



Phenylalanin. Tyrosin. 



n H n H 



HOV HOV 



CH 2 COOH CH 2 CH(OH)COOH 



Homogentisinic acid. Uroleucic acid. 



What changes aromatic acids undergo in the body in cases of 

 alcaptonuria has been carefully studied by Neubauer and Falta, 1 who 

 point out that a-phenyl-propionic acid behaves like phenyl-alanin and 

 tyrosin in increasing the output of homogentisinic acid. 



Baumann and v. Udranszky, Abderhalden, and Abderhalden and 

 Falta have proved that alcaptonuria, cystinuria, and diaminuria are due 

 to abnormalities in the metabolism and not due to intestinal putrefaction. 

 The occurrence of amino-acids in the urine in cases of phosphorus 

 poisoning and in acute yellow atrophy of the liver is also dependent 

 on faulty metabolism. 2 



Drechsel 3 has found cystin also in the normal liver. The taurin 

 of the bile is a derivative of cystin. 4 See p. 59. 



By analogy we may further reason that all substances which on 

 introduction into the body do not become oxidised, are not produced 

 in metabolism (Cohnheim). 



The carbohydrate-radical of albumins is discussed on p. 154. 



Nothing is known as to relationship of albumins to oxyproteic 

 acid, 5 uroproteic acid, 6 and uroferric acid, 7 substances which have 

 been found in the urine. 



1 Otto Neubauer and W. Falta, Zeitschr. f. physiol Chem. 42. 81 (1904). 



- E. Abderhalden and P. Bergell, ibid. 39. 464 (1903). 



:1 E. Drechsel, Arch.f. (Anat. u.} Phys. 1891, p. 243 ; Zeitschr.f. Biol. 33. 86 (1896). 



4 G. v. Bergmann, Hofmeisters Beitr. 4. 192 (1903) ; see also J. Wohlgemuth, 

 Zeitschr. f. physiol. Cliem. 40. 81 (1903). 



5 Bondzynski and K. Gottlieb, Centralbl. f. d. med. Wissensch. 1897, p. 577; F.' 

 Pregl, Pfluger's Arch. f. d. ges. Physiol. 75. 87 (1899) ; Bondzynski and K. Panek, Ber. 

 d. deutsch. chem. Ges. 35. II. 2959 (1902). 



6 M. Cloetta, Arch. f. exper. Path. u. Pharm. 4O. 27 (1897). 



7 0. Thiele, Zeitschr. f. physiol. Chem. 37. 251 (1903). 



