OXIDASES OR OXIDISING ENZYMES. 265 



solution, it was precipitated by addition of 400 cc. of 

 alcohol and pressed dry. It was further purified by a 

 repetition of this treatment. Dried at 35° C. it weighed 

 about 7 gms. This precipitate yielded to cold water after 

 some hours maceration, a principle which oxidised tyrosin 

 rapidly, but had hardly any perceptible action on either 

 hydroquinone or pyrogallol. 



Tyrosinase is destroyed at a much lower temperature 

 than laccase, being injured at about 50° C. and more rapidly 

 at higher points ; it is possible thus to prepare laccase alone 

 from a mixture of the two, by heating the liquid containing 

 them to 70° C. It then oxidises hydroquinone, but is 

 without action on tyrosin. 



Bourquelot (16) has recognised tyrosinase in many 

 genera of fungi, among which may be mentioned Boletus, 

 Rtissula, Lactarius, Paxillus, Coprinus, Psalliota, Hebeloma, 

 Pholiota, Collybia, Clitocybe, Tricholoma and Amanita ; in 

 all these it is associated with laccase, but in the case 

 of Amanita the latter enzyme is present only in small 

 quantities. 



Besides oxidising tyrosin, Bourquelot (17) has found 

 tyrosinase to act on all the cresols, resorcinol, guaiacol, 

 metatoluidine, xylidine, ortho-, meta-, and para-xylenol, 

 thymol, carvacrol, and a and /3 naphthol. He has noted a 

 further peculiarity in its behaviour in that it is effective 

 when dissolved in a mixture of water and either ethyl or 

 methyl alcohol, provided that not more than 50 per cent, of 

 the spirit is present. The alcohols themselves are not 

 affected by it. 



CENOXYDASE. 



Another of these oxidising enzymes has been dis- 

 covered to play a prominent part in causing a particular 

 disorder in certain wines to which the name " casse " or 

 " cassure " has been applied. According to BoufTard (18) 

 a wine affected in this way loses its characteristic colour, and 

 after three or four hours it contains a red-brown precipitate. 

 If the wine is at rest the decoloration begins at the surface 

 where a thin pellicle of colouring matter forms, and gra- 



