1913] Johnson: Pigment Formation in Amphibian Larvae 77 



anhydride and glycyl-tyrosin anhydride, giving rise to yellow 

 substances which do not become black as does tyrosin itself. 

 However, a mixture a glycyl-tyrosin anhydride with glycin gives 

 with tyrosinase a rose color changing to bluish green, with alanin 

 it gives a deep red, and with leucin a deep brown color. 



Abderhalden and Guggenheim (1907) studied the action of 

 tyrosinase from Russula delica on tyrosin and various tyrosin- 

 containing polypeptids. Aspartie and glutaminic acids and other 

 amino acids inhibited the action, especially if they were present 

 in strong solution. Polypeptids containing tyrosin residues were 

 colored by tyrosinase, the color being somewhat modified by the 

 nature of the amino acid combined with the tyrosin in the poly- 

 peptid. They conclude that the character of the pigment result- 

 ing from the action of tyrosinase on tyrosin is dependent upon 

 the combination in which the tyrosin exists. 



Table 10 



Cleavage products of certain animal and vegetable proteids; ovalbumin, 

 vitellin, and gliadin taken from Hammarsten (1911), gluten from 

 Plimmer (1908). 



'Abderhalden and Malengreau; Kossel and Kutscher. 



