Chapter III. 
THE PEROXIDASES AND CATALASES. 
In addition to the oxidases, two other classes of enzymes are more 
or less immediately concerned in the oxidation processes occurring 
in the plant and animal. These are the peroxidases and catalases. 
These have been found to have even a wider distribution among 
living cells and tissues than the oxidases. They were called by Bour- 
quelot ( 83 ) the “indirect oxidizing ferments." It was known to 
Schoenbein ( 383 ) that many substances of animal and vegetable ori- 
gin which in themselves are incapable of bluing guaiacum, acquire 
this property when mixed with hydrogen peroxide. In other words, 
just as certain extracts and tissues have the power of rendering active 
the oxygen of the air, so certain others possess the property of ren- 
dering active the oxygen of hydrogen peroxide, thereby enabling this 
compound to effect certain oxidations which ordinarily it is inca- 
pable of bringing about. Thus on adding a small amount of extract 
of malt to a mixture of guaiacum and hydrogen peroxide the mixture 
rapidly becomes blue in color. He also made the interesting obser- 
vation that many plant and animal tissues and the extracts thereof 
and many hydrolytic ferments Jiave the power of effecting the de- 
composition of hydrogen peroxide into water and oxygen. He seems 
to have regarded the power to render active the oxygen of hydrogen 
peroxide and the power to catalyze this substance not as specific 
activities of any given substances but as properties pertaining to the 
ferments as a class. In other words, the power to oxidize guaiacum 
by means of hydrogen peroxide and the power to decompose the 
latter substance into water and oxygen were looked upon by him 
simply as properties of diastase, emulsin, myrosin, and other fer- 
ments. This view prevailed for a long time and was shared by others. 
Thus, according to Spitzer ( 407 ), the power to decompose hydrogen 
peroxide is a measure of the oxidizing power of various animal tis- 
sues. It was afterwards shown by Raudnitz® ( 338 > 339 ), however, that 
the substance in milk which gives the guaiacum reaction with hydro- 
gen peroxide is really different from the other substances present in 
milk, in that it conducts itself differently toward various precipi- 
tant^; and Jacobson ( 223 ) pointed out that the power of any given 
a Raudnitz ( 339 ) called the catalase of milk a superoxydase, and the guaiacum-bluing 
ferment a globulin-oxydase. ^ Jd 
( 108 ) 
