ON MELANIN 



ROSS AIKEN GORTNER 



{Biochemical Laboratory of the Station for Experimental Evolution, The Car- 

 negie Institution of Washington, Cold Spring Harbor, L. I.) 



I. INTRODUCTION 



Although the literature concerning the animal pigments is very 

 extensive it is noteworthy that the work is not comparable owing 

 to the great diversity of the methods by which the pigments were 

 isolated. Great difference of opinion is also observed as to the ease 

 with which melanins are decomposed, some authors claiming that 

 boiling with concentrated acids does not alter their composition 

 while others State that they are profoundly changed by the action 

 of acids. The study of these pigments has, therefore, been taken 

 up at this Station with the view of thoroughly investigating the 

 nature of the melanin molecule and the reaction by which these 

 pigments are formed in the animal body. The present paper is a 

 report of some of the work which has already been completed. 



IL THE CHEMISTRY OF MELANIN FORMATION 



In 1896 Bertrand discovered a new type of oxidase which 

 appears to be a true enzyme. He noted that this ferment was ca- 

 pable of oxidizing tyrosin through various colors to a black precipi- 

 tate, and, therefore, gave to this type of oxidases the generic name 

 of tyrosinase. Later, von Fürth (1902) summed up the instances 

 where tyrosinases were known to occur in the animal kingdom and 

 suggested that perhaps the melanins were the product of the inter- 

 action of this ferment and tyrosin. Almost coincident with the pub- 

 lication of von Fürth's theory confirmatory evidence was furnished 

 by Dewitz (1902) who found that the pigmentation of the fly 

 (Lucilia Caesar) was caused by the action of a tyrosinase on a 

 chromogen. Roques (1900) showed that a similar action occurred 

 during the metamorphoses and pigmentation of a beetle (Limno- 



207 



