- 3 6- 



Loew 42 reports two kinds of enzymes, an insoluble and a 

 soluble form a- and ^-catalase respectively. The former is prob- 

 ably a compound of the soluble catalase with a nucleoproteid. 

 while the soluble catalase is an albumose and can be liberated by 

 the action of very dilute alkaline media upon the insoluble cata- 

 lase. He has studied these enzymes with special reference to the 

 tobacco plant. 



Catalase does not color tincture of guaiac blue, but changes 

 hydroquinone into quinone. Traces of acids increases its action 

 while alkalies destroy it. 



Chodat and Bach 43 state that catalase is not a true enzyme 

 like oxydase or peroxydase, as its function is only to decompose 

 hydrogen peroxide. 



Kastle and Shedd 44 have shown that phenolphthalin is oxi- 

 dized to phenolphthalein by oxidizing ferments and that it forms 

 a very sensitive reagent for the presence of soluble enzymes. 

 They have tested this reagent upon a number of enzymes from 

 plants and on a few from animals. These results were com- 

 pared with those obtained by tincture of guaiac and found to be 

 practically identical, i. e., all those enzymes which gave a blue 

 color with guaiac, gave a pink color with phenolphthalin, the 

 colors in both cases increasing or decreasing with the activity 

 of the enzyme. 



In i8c)8 45 L,aborde proposed to measure the activity of en- 

 zymes by comparing the color produced by the enzyme when act- 

 ing upon an alcoholic tincture of guaiac, with a standard color 

 formed by adding 0.5 gramme of iodine to 20 cc. of the tincture 

 of guaiac. 



Alliot and Pozzi-Escot 48 found it impossible to estimate oxy- 

 dases colorometrically either by Laborde's guaiac method or by 

 Kastle and Shed's phenolphthalein method. 



Kastle and Shed found that the only enzyme obtained from 

 animal source, which acted as an oxidizing enzyme was the 

 human saliva. 



About this time Cavazzani 47 found a soluble oxidizing en- 



42 U. S. Dept. of Agriculture, Report No. 68, 1901. 



M 



Am. Chem. Jour. 26, 1901, p. 526. 

 45 Compt. rend. 126, 1898, p. 536. 

 ** Ann. Chem. Anal. 7, 1902, p. 210. 

 41 Cent. Physiol. 14, 1901, p. 473. 



