1916] REED—PEROXIDASES 237 
subjecting the peroxidase to the oxidizing action of the permanga- 
nate at sufhciently frequent intervals, it is apparent that the reaction 
could be made to proceed as rapidly as the curve OC (fig. 2), which 
represents the hydrogen peroxide reaction catalyzed by untreated 
peroxidase. 
Hence we may conclude that just as platinum is recharged with 
oxygen by hydrogen peroxide, as soon as some of the oxygen has 
been removed from the platinum by a reducing agent, so the horse- 
radish peroxidase is recharged by hydrogen peroxide under similar 
conditions. 
An investigation of potato peroxidase gave exactly similar 
results. It may be of interest to note that by treating the peroxi- 
dase from the inner tissues of the potato with permanganate it could 
be made to behave like the oxidase (that is, peroxidase in combina- 
tion with the oxygenases) from the outer part of the tuber. 
It may be concluded, therefore, that in oxidation processes 
catalyzed by peroxidases two reactions are involved. The peroxi- 
dase combines with oxygen from the oxygenases (or from hydrogen 
peroxide, or possibly from some other source, since it is capable of 
taking it from potassium permanganate) to form an intermediate 
compound which is a more energetic oxidizing agent than the 
original source of the oxygen. The final stage in the oxidation is 
then affected by this intermediate compound. 
A new light is thus thrown on the mechanism of oxidation in 
living tissues which has so long proved baffling to investigators. 
The difficulties which beset this field of research are clearly illus- 
trated by the fact that a great amount of careful investigation 
was necessary before the conceptions of oxygenase and peroxidase 
could be established. The next step was to elucidate the con- 
nection between these entities. This now seems to be accomplished, 
but it would probably not have been done so soon or so satisfactorily 
without first making a careful study of the simpler conditions to be 
found in oxidations which are catalyzed by platinum. 
In this connection it is of interest to recall that VAN SLYKE and 
CULLEN‘ have shown recently that in the fermentation of urea by 
soy bean urease there is a combination between urea and ferment 
4Van StykeE, D. D., and Cutten, G. E., Jour. Biol. Chem. 39:141-180. 1914. 
Pie 
