OXIDASES OR OXIDISING ENZYMES. 261 



action. It gave also the reactions just described with laccol, 

 pyrogallol, etc. 



When the extract so prepared was boiled it gradually lost 

 its enzymic powers. Bourquelot and Bertrand say however 

 that it is more resistant to heat than most enzymes, and that 

 to ensure complete destruction the boiling should be main- 

 tained for a short time. 



When the extract of Russula is poured into an excess 

 of alcohol it yields only a small amount of precipitate, but 

 this when separated off gives up the enzyme to cold 

 distilled water. The precipitation of the laccase is not 

 complete however when the extract is treated in this 

 manner. 



A very large number of species of fungi have been ex- 

 amined, chiefly belonging to the Basidiomycetes, more than 

 half of which have been found to contain laccase, capable of 

 acting on the aromatic bodies mentioned. Of these the 

 genera Russula, Lactarius, Boletus, and Psalliota are the 

 most noteworthy. The Gasteromycetes as a rule contain 

 little if any, and the Ascomycetes and Myxomycetes, so far 

 as they have been examined, are free or nearly free from 

 the enzyme. 



Besides working at the effect of laccase on the aromatic 

 bodies as described above, Bourquelot and Bertrand inves- 

 tigated the nature of the changes of colour which supervene 

 when many of the fleshy fungi are cut and the damaged sur- 

 faces exposed to the air (11). The tissue of Boletus almost 

 instantaneously changes under such conditions, assuming a 

 blue colour, the depth of tint and rapidity of appearance 

 varying somewhat in different species. Lactarius becomes 

 violet when wounded, while Russula turns first red and 

 finally black. 



There have been several theories as to the cause of this 

 change of colour. Schcenbein (12) so long ago as 1856 

 noticed the phenomenon, and he attributed it to the action 

 of ozone upon a particular chromogen in the fungus, saying 

 that the latter also contains a substance capable of trans- 

 forming the oxygen of the air into ozone. In 1872 Lud- 

 wig made some investigations into the subject, and con- 



