ie oe ee ae eel 
19 
tive substance on heating to from 71° to 75° C. The degree of tem- 
perature at which the enzym is ‘*killed” depends upon the time of 
exposure. At 72° C. more than fifteen minutes are required, while a 
much shorter time suffices at 74° C. Heating but for a second to 75° is 
not sufficient to kill all the enzym ina neutral solution, but it will injure 
a great part of it. Ina very weak alkaline solution the killing tem- 
perature is raised several degrees, but the contrary is true when this 
alkaline reaction is increased still a little more. In slightly acidulated 
solutions the killing temperature is lower than in neutral ones. 
The killing temperature of @-catalase is about the same as that of 
f-catalase. Green tobacco leaves were crushed and the juice expressed 
through flannel. This turbid liquid of acid reaction was passed through 
a filter, and the filter content, rich in a-catalase, suspended in water and 
heated to various temperatures. Heating for ten minutes to 60° C. did 
not decrease the intensity of the catalytic power, but heating for five min- 
utes to 71° C. injured it considerably. After heating for five minutes 
to 75° C. and cooling quickly a faint trace of that power was still 
observed, but no trace was noticeable after heating for one minute to 
SO-. The filtered liquid in the latter case still contained considerable 
active peroxidase, another proof that this enzym can not be identified 
with catalase. | 
In a dry condition catalase resists.heat better than in the presence of 
water. For example, fermented tobacco leaves when heated for two 
hours to 100° C. had not completely lost their content of @- and /-cata- 
lase, although it was very much decreased. A prolonged application 
of heat, however, kills these enzyms at 80° C., even in the absence of 
water, as may be inferred from the inactivity of fire- and flue-cured 
tobacco (cigarette tobacco). Various samples of such products were 
tested, and in most cases no trace of either a- or /-catalase could be 
observed. 
EFFECT OF MECHANICAL MOTION ON THE REACTION WITH HYDROGEN 
PEROXID. 
s 
It is remarkable to what extent the action of the soluble catalase is 
promoted by shaking the mixture. One out of many of the observa- 
tions may be mentioned here. A cold-prepared aqueous extract of 
sweated tobacco (20 cc.) was mixed with half its volume of hydrogen 
peroxid and the flask left untouched. In the control case the flask was 
continuously shaken. The amount of oxygen developed in thirty min- 
utes, not shaken, was 24 cc.; shaken, was 51 cc. The oxygen developed 
under the influence of mechanical motion was therefore more than 
double the amount obtained when the flask was left undisturbed.! 
‘It hardly needs to be mentioned that in all experiments described in this paper the 
mixtures with hydrogen peroxid were frequently shaken during the observations in 
order to obtain the full reaction. Heating the mixtures was never resorted to; on the 
contrary, any rise of temperature was avoided. 
