﻿THE SIGNIFICANCE OF COLOR CHANGES IN OXIDASE 

 REAGENTS 



Our knowledge of the oxidases has been derived almost entirely 

 from the study of their action upon compounds which change color 

 on oxidation. It is customary to employ for this purpose com- 

 pounds which do not oxidize spontaneously (or do so very slowly) 

 when exposed to the air in dilute solutions, but which when brought 

 into contact with living tissues (or extracts of tissues) exhibit a 

 change of color. 



The formation of such colored compounds as a result of oxidase 

 action has afforded a ready method of determining the distribution 

 of these ferments. The behavior of the various indicators when 

 placed in contact with different tissues has also led to the conclusion 

 that the oxidases may be divided into several more or less definite 



The rate of oxidase action and the relative efficiency of different 

 preparations of oxidases have also been determined by measuring 

 the intensity of the color produced in solutions of such indicators. 1 



Valuable as these methods have been, they have given no indi- 

 cation of the amount of oxidation which has taken place. Thus, 

 when an oxidase causes a change of color in one of these reagents 

 we have no idea of the amount of oxidation which this reaction 

 represents. Moreover, it often has been assumed that the appear- 

 ance of a definite color in any of these reactions, acted upon by the 

 oxidases, represents similar amounts of oxidation. For example, 

 an oxidase capable of bringing about sufficient oxidation to give a 

 distinct blue color in a solution of gum guaiac has been considered 

 about as efficient as one capable of producing enough purpurogallin 

 to give a distinct yellow color in a solution of pyrogallol. 



Inasmuch as the greater part of the results obtained by workers 

 on oxidase reactions depend upon these color changes, it is important 



oxidase action have recently been reviewed by FoA, Biochem. Zeit. 2: r 1 



and also by Bunzell, Bull. no. 238. Bur. PL Ind., Washington. 191 1. 



Botanical Gazette, vol. 61] [43° 



