OXIDASES OR OXIDISING ENZYMES. 259 



out the sap, which was then saturated with chloroform and 

 allowed to stand in the dark for twenty-four hours. The 

 juice was next filtered and 2\ volumes of alcohol added to 

 precipitate the laccase. The precipitate was taken up with 

 a little water, the solution filtered and the laccase aeain 

 thrown down by large excess of alcohol. The final pre- 

 cipitate was collected and dried in vacuo. It contained a 

 mere trace of manganese. 



To 50 cc. of a solution of hydroquinone *i gm. of this 

 precipitate was added, and the whole was agitated for 

 twenty-four hours in contact with air. There was then only 

 a red coloration produced. To a further quantity of 50 

 cc. of the hydroquinone solution 'i gm. of the precipitated 

 laccase and 1 mgr. of manganese in the form of the sul- 

 phate were added together, and in as short a time as two 

 hours crystals of quinhydrone were formed. In the latter 

 case there was an evident oxidation, much more extensive 

 than after twenty-four hours' agitation in the absence of the 

 manganese. 



In an experiment so arranged that the absorption of 

 oxygen could be measured, it was found after six hours' 

 agitation with air at 15° C. that with laccase alone '2 cc. 

 oxygen were taken up ; with a salt of manganese alone "3 

 cc. were absorbed, but with both present together 6*3 cc. 

 of oxygen were fixed. 



The manganese is thus seen to play a very active part 

 in the ordinary action of the enzyme. No other metal has 

 been found to be capable of replacing it. 



Manganese combined with various acid radicals was 

 found in a further series of -experiments to have a certain 

 power of causing oxidation of hydroquinone, the protoxide 

 appearing to act as a carrier of the oxygen (9). Comparing 

 the action of these salts of manganese with the conjoint 

 action of manganese and laccase, Bertrand advances the 

 theory that the oxidases can be conceived to be special 

 combinations of manganese with certain proteid bodies con- 

 taining acid radicals, the latter varying with the particular 

 enzyme. In such combinations the acid radical has just the 



necessary affinitv to keep the metal in solution. The work 



18 



