27 
ACTION- OF FORMALDEHYDE. 
Fifty ec. of a weak alkaline solution of @-catalase were mixed with 
10 ec. commercial formalin’ previously neutralized. Of this mixture 
20 cc. were immediately mixed with 5 cc. hydrogen peroxid, the amount 
of oxygen developed in ten minutes being as follows: 
A diluted solution of @-catalase was mixed with 10 per cent of neu- 
tralized formalin, causing the formation of some precipitate. After 
twenty minutes 20 cc. were mixed with 5 ec. hydrogen peroxid and 
still 1 cc. oxygen was obtained, but after standing one hour no trace 
was produced. In the control case 44 cc. were developed in ten 
minutes. 
ACTION OF NITROUS ACID. 
Neither a-nor f-catalase is injured by a 5 per cent solution of sodium 
nitrite at the ordinary temperature within one day, provided the solu- 
tion is neutral or weakly alkaline, but as soon as the mixture is acidu- 
lated the enzym is injured by the nitrous acid liberated. 
A special test showed that 0.4 per cent free nitrous acid injured the 
-enzym considerably in one day. QOne-tenth gram of crude catalase 
was dissolved in 100 cc. water. Chloroform was then added and the 
solution shaken and divided into three equal parts. One part received 
no addition. The second part received an addition of 0.2 gram of 
acetic acid, and the third part 0.2 gram of acetic acid and 0.22 gram of 
sodium nitrite. After standing one day these solutions were made 
slightly alkaline before 5 cc. of hydrogen peroxid were added. The 
volumes of oxygen developed in 14 minutes were: 
Ce. 
een eae ee ee A, te i tt a ote Se Wa ns SO 40 
eT tes a CR eS ee 8.4 
Aster ease ert) ag eG == |. oe ere 2 ne ee eee phe 
The loss of activity under the influence of formaldehyde or of nitrous 
acid renders the supposition very probable that labil amido groups are 
concerned in the activity of the enzym, since labil amido groups are 
very readily acted upon, even in neutral and highly dilute solutions, 
by those compounds.* Here we have before us a specific action, while 
the loss of activity under the influence of hydrochloric, sulphuric, or 
1 The preparation contained about 40 per cent pure formaldehyde and had only a 
slightly acid reaction. It may be mentioned that this aldehyde in dilute and neu- 
tral solution is acted upon but slowly by hydrogen peroxid; hence this influence 
can be neglected here. 
?The detrimental action of mercuric chlorid above mentioned might most easily 
be explained by the reaction of this salt upon labil amido groups in which hydrogen 
can easily be replaced by mercury. By such a chemical change of an acuve atomic 
group the activity of the enzym itself is inhibited or destroyed. 
