Plant oxydases and the chemical interrelationships of colour-varieties. 461 



it is to them we owe the greater part of our present knowledge of 

 oxidising" enzymes. 



On the basis of their theory, two components are essential to 

 the constitution of an oxydase and these have been termed peroxide 

 and Peroxydase respectively. Many plants, according to Chodat 

 and Bach, contain organic bodies, capable of autoxydation, that is 

 of annexing an extra oxygen atom, thereby becoming organic peroxides, 

 analogous in constitution to hydrogen peroxide. This superoxidation 

 may sometimes be brought about through the agency of an enzyme, 

 in which case a new term is used for the autoxydator, i. e., oxygenase. 

 Both oxygenase and Peroxydase have properties in common with other 

 ferments, that is they are destroyed by heat, precipitated by alcohol, 

 are soluble in water, etc. Whereas the function of the oxygenase 

 is to reactivate the peroxide after reduction that of the Peroxydase 

 is to reduce the peroxide, transferring its extra oxygen atom to 

 bodies of an oxidisable nature in the plant so that heat and energy 

 may be liberated. Such a body, and one which may be used arti- 

 ficially as an acceptor of oxygen, is guaiacum. A solution of guaiacum 

 in alcohol is yellowish in colour but the addition of a small quantity 

 of oxydase solution immediately produces an intense blue colour. The 

 oxydase has all the necessary mechanism for transferring molecular 

 oxygen from the air to the oxidisable guaiacum; the Peroxydase, 

 however, can only blue guaiacum when a peroxide, such as hydrogen 

 peroxide, is artiflcally supplied. 



Certain results obtained by fractional precipitation of oxydases 

 with alcohol, support the idea of their dual nature. Chodat and 

 Bach found, for instance, that the oxygenase in the sap of Lactarius, 

 one of the Basidiomycetes, was largely precipitated by 40 per cent 

 alcohol, while the Peroxydase remained in solution. The isolated 

 portions were inactive or very much weakened, but the activity 

 returned on recombining the constituents, 



I have found the oxygenase component to be more sensitive to 

 the action of absolute alcohol than the Peroxydase. When tissues 

 containing an oxydase are treated with absolute alcohol, the longer 

 the exposure, the weaker the guaiacum reaction becomes, until it 

 entirely disappears, though the Peroxydase can still be detected on 

 addition of hydrogen peroxide. 



