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‘ 
THE MODE OF ACTION OF PLANT PEROXIDASES 
G: BB. REED 
(WITH TWO FIGURES) 
In a recent paper’ it was shown that while colloidal platinum 
markedly accelerates the rate of oxidation of various substances 
by hydrogen peroxide, it does not ordinarily bring about oxidation 
in the absence of hydrogen peroxide. Experiments were described, 
however, which show that when the colloidal metal is charged with 
oxygen (by making it an anode) it rapidly brings about a certain 
amount of oxidation. By repeating the charging process at 
sufficiently frequent intervals colloidal platinum might be made 
to bring about the oxidation of various substances at a rate approxi- 
mating that affected by hydrogen peroxide and colloidal platinum. 
From this it was concluded that the action of the colloidal metal in 
accelerating oxidation by hydrogen peroxide (that is, its peroxidase 
action) is due to the taking of oxygen from the peroxide by the 
metal to form a compound which is a more efficient oxidizing agent 
than the original peroxide. 
This information, gained from a study of a simple peroxidase 
reaction where the constitution of the catalyzer was known, has 
made possible an analogous investigation of the more significant 
and complicated problem of the nature of the peroxidases produced 
Jn living tissue. Since, as has frequently been pointed out, the 
peroxidase action of colloidal platinum closely resembles that of 
the plant peroxidases, it seemed probable that the mechanism of 
the reactions must besimilar. Accordingly, the experiments which 
proved fruitful in a study of the platinum reaction have been 
repeated, as nearly as the material permitted, with certain plant 
peroxidases. 
The very active ferment of horseradish root was first investi- 
gated. About 150 gm. of the finely chopped tissue was mixed with 
twice its volume of distilled water and allowed to stand for 24 
* REED, G. B., Mechanism of oxidase action. Bot. Gaz. 62:53-64. 1916. 
233] [Botanical Gazette, vol. 62 
