2ig BOTANICAL GAZETTE [march 



Historical 



Berteand (5) was the first investigator to point out that the 

 salts of metals influence oxidase activity. He showed that man- 

 ganese salts greatly increase the oxidase activity of preparations 

 from alfalfa. Gessard (15) found that the formation of melanin 

 from tyrosin is increased in the presence of salts of the metals. 

 Bach (4) substantiated Gessard's results, and showed that 

 aluminum sulphate, salts of calcium, magnesium, manganese, 

 and zinc increase melanin formation from tyrosin. The effect of 

 the salts is to increase the further change of the oxidation product 

 rather than to activate the taking up of oxygen. Aluminum 

 salts hasten the formation of purpurogallin from the yellow 

 oxidation product of the action of oxidase upon pyrogallol. Bach 

 believed that the oxidation process is retarded by the accumula- 

 tion of the primary oxidation products, and that the salts act 

 to release them. Wolff (32) found that the oxidation of tyrosin 

 by tyrosinase from Russida delica is increased by the addition 

 of small quantities of disodiumphosphate. Porodko (26), Aso (3) , 

 Alsberg (2), and Ewart (ii) have shown that salts of the metals 

 give a blue color with guaiacum. Porodko and Ewart believed 

 these salts to be inorganic oxidases. Porodko pointed out that 

 those metals which form salts of two degrees of oxidation are par- 

 ticularly active. Alsberg, and also Ewart, confirmed Porodko's 

 observation and found that the chlorides of many of the met- 

 als give a blue color with guaiacum. Alsberg attributed an 

 important part in the reaction to the chlorine. Ewart further 

 found that the chlorides, nitrates, and sulphates of the same metal 

 are not necessarily equally powerful in their action. Apparently 

 the chlorides are more active than the sulphates. Various salts 

 were found to act as sensitizers or retardants to oxidase activity. 

 Potassium chloride, potassium iodide, potassium bromide, and 

 potassium fluoride retard or even prevent the browning of pounded 

 apple pulp. 



Numerous investigators have shown that oxidase activity is 

 affected by changes in reaction of the medium. Bertrand (6) 

 showed that the action upon guaiacol of laccase from Rhus succe- 

 danea is inhibited by 0.002 M concentration of sulphuric acid. 





