Il6 SCIENCE PROGRESS 



It should be mentioned that the production of the organic 

 peroxides before alluded to is by some held to be the work of 

 a special enzyme oxygenase. 



It has been pointed out by Bertrand ' that the aromatic 

 monophenols and monamins are not easily oxidised by laccase, 

 but that substances which it readily attacks are all members 

 of the benzene series containing hydroxyl or amino groups 

 in the ortho or para positions. 



Researches in plant physiology deal almost entirely with 

 the two classes of enzyme at the head of the list ; there is 

 at present no proof that the laccase or tyrosinase from one 

 species is identical with that from another, though they may 

 produce certain colour reactions in common. This important 

 question is being investigated by Bunzel. The part played 

 by inhibitors in effecting apparent specific action by oxidases 

 will be treated of later on. 



For further information, concerning the preparation of 

 artificial oxidases, the effect of small quantities of acids, alkalis 

 and manganese salts upon the activity of oxidases, as well 

 as for discussions of the identity of Medicago-oxidase with a 

 mixture of calcium salts of organic hydroxy acids including 

 glycollic, citric, malic and mesoxalic, the reader is referred 

 to the monographs by Kastle and by Clark, and to Euler's 

 General Chemistry of the Enzymes. 11 



The Physiological Functions of the Plant Oxidases 



Respiration.— It is a matter of common observation that 

 leaves when killed by frost or by severance from the tree 

 frequently assume a brown, black or red colour, and that 

 local injuries such as punctures by insects or by parasitic 

 iungi take on similar shades of pigmentation. The conspicuous 

 purple red spots appearing on blackberry leaves in autumn 

 are a good example of the effect of the last-mentioned cause, 

 being brought about by the disorders in metabolism due to 

 the attack of Phragmidium violaceum, the teleutospores of which 

 are always found as black specks on the lower surfaces of 

 leaves which show such discolorations. 



Numerous investigators have established the fact that these 



1 Bertrand, C. R. 1896, 122, 1132. 

 * Wiley & Sons, New York, 1912. 



