28 



fractions of different manganese contents, which with hydroqui- 

 none solutions showed activities proportional to their percentages 

 of manganese. Bearing this in mind, other investigators have 

 used mixtures of protein substances and manganese salts to 

 prepare artificial oxidases giving many of the reactions of the 

 natural preparations. It should be noted, however, that Bach 

 and other investigators have prepared oxidases from various 

 plants which, although active, did not contain manganese or 

 iron. 



During the last year, Euler and Bolin^ have shown that the 

 laccase prepared from alfalfa {Medicago sativa) is not an enzyme 

 according to the commonly accepted usage of the word. They 

 found that heating did not destroy the activity of the oxidase, 

 and that the protein thus precipitated could be filtered off without 

 lowering the activity in the least. This so-called laccase proved 

 to be mostly calcium glycollate, with traces of the calcium salts 

 of citric, malic, and mesoxalic acids. 



If, as Bach and Chodat say, laccase consists of organic perox- 

 ides activated by the enzyme peroxidase, then it is the peroxidase 

 part which confers upon laccase what specificity it has. How- 

 ever, laccase is not a specific enzyme in the narrow sense because, 

 besides the laccol of Rhus spp., it will oxidize guaiacol, hydro- 

 quinone, guaiac tinctiire, phenolphthalin, and many phenols and 

 cyclic amino derivatives; still, it is not able to oxidize tyrosin or 

 any of the tyrosin derivatives upon which tyrosinase exerts a truly 

 specific action. So then, laccase is a specific enzyme, in that it 

 acts only upon substances containing a certain grouping in their 

 structure. The fact that laccase acts upon guaiac tincture and 

 upon many other reagents usually employed to detect peroxidases, 

 etc., makes one skeptical in regard to the nearly universal occur- 

 rence of laccase claimed for it by the earlier investigators. 



Tyrosinase 



After Bertrand and Bourquelot had shown that the bluing of 

 Boletus cyanescens upon injury was due to the effect of laccase 

 acting with the atmospheric oxygen upon the "boletol" in the 



^ Loc. cit. 



