960 SCIENCE. 
pepsin, while it does not injure diastase or 
oxidase. Atropine in moderate quantities 
makes diastase inactive.* Further, pro- 
longed contact with alcohol injures the en- 
zymes more or less. 
The writer long ago tried to solve the 
question what kind of labile atomic groups 
cause the activity of enzymes, and had cer- 
tain reasons for the supposition that the 
lability is due to the simultaneous pres- 
ence of aldehyde and amido-groups in the 
molecule of an enzyme. Indeed amido- 
aldehydes (and amido-ketones) exhibit a 
high degree of lability. The usual tests for 
aldehyde groups failed however, but it may 
nevertheless be possible that these are pres- 
ent in the less active polymeric form.+ I¢ 
deserves to be mentioned in this connection 
that free hydroxylamnie which very easily 
enters into reaction with aldehyde groups, 
also renders diastase inactive in a diluted 
neutral solution. In regard to labile amido- 
groups it is to be expected that enzymes 
containing them would become inactive as 
soon as certain compounds combine with 
the amido-groups and change them. Such a 
substance is formaldehyde. Indeed, pepsin 
and diastase are rendered inactive when 
they remain for’24 hours in contact with a 
neutral solution of 5 per cent. formaldehyde. 
Other enzymes, as emulsin, papayotin, tryp- 
sin, etc., yield in its presence inactive precip- 
itates.{ These observations were later on, 
made also in the Institut Pasteur without, 
however, any attempt to draw a further in- 
ference. In the opinion of the writer how- 
ever, this behavior makes the presence of 
labile amido-groups highly probable. 
If we now take into consideration the 
* Detmer, Landwirthshaftliche, Jahrbiicher, 1881. 
+ Nencki and Macfadyen observed with one enzyme 
only, viz., one derived from the cholera bacillus, a re- 
duction of an alkaline silver solution (1891), while 
Brieger obtained a phenylhydrazone with a protein 
contained in a culture of the microbes of diphtheria, 
{ O. Loew, Journ. f. prakt. Chem., Vol. 37, p. 704 
(1888). 
[N. S. Vou. X. No. 261. 
fact that the study of the cleavage pro- 
ducts, obtained by boiling with acids or 
alkalies, or the elementary analyses, can 
only clear up the composition of the killed 
enzymes, while it leaves us completely in the 
dark as to the nature of the labile active 
groups in the original enzymes, we must feel 
surprised at the attempts to find by simple 
analysis the true nature of the chemical 
power of enzymes. 
The denial of the protein nature of en- 
zymes on the ground that they are more 
easily changed by injurious influences than 
are the proteins is also a source of surprise. 
Several passages may here be quoted to 
show the opinions of recent physiologists. 
Thus we find in an article by a German 
physiologist the following passage: ‘“‘ There 
is no reason to doubt that as soon as an 
analysis of the enzymes has been accom- 
plished, their synthesis will be accom- 
plished too.”” And in a recent work of an 
English physiologist we read: ‘‘ Some seri- 
ous objections to the view that enzymes are 
proteids can be based upon the action of 
light upon them. Diastase is injured by 
direct sunlight, proteids are not.” Both 
these views are unqualifiedly erroneous. Enzymes 
of protein nature are not ordinary passive 
proteins, but proteins with labile atomic 
groups. Only the changed (killed) enzymes 
can be classified with the ordinary proteins.* 
As soon as we understand the close con- 
nection between lability and activity, and 
that enzymes are capable of transforming 
heat energy into chemical energy, we can 
also by means of Helm’s principle of the 
intensity of energy understand that their 
chemical energy may be transferred to 
other compounds. And when these other 
compounds are of such a character that 
* The writer makes use of the proposed distinction 
between protein and proteid. Protein is the general 
name for all protein matter, while proteid signifies 
exclusively the more complicated kinds containing 
phosphoric acid, sugar, etc. (nucleins, mucins, ete. ). 
