DECEMBER 29, 1899. ] 
properties of enzymes. Although an in- 
crease of heat up to a certain point (the 
optimum temperature) promotes their ac- 
tions, a further rise in temperature is in- 
jurious and a still further rise stops all 
their actions. This is in perfect accor- 
dance with the transition of a labile to a 
stable modification, or even to a still 
more different compound, produced by 
atomic migrations. The labile atoms ap- 
proach by their larger oscillations too 
closely to other atoms, the affinity of which 
can exert now sufficient power to produce 
an ‘atomic migration.’* The enzymes are 
‘killed’ at this fatal degree of intensity of 
heat, in other words they have lost their 
labile, unstable atomic groups, by ‘ migra- 
tion’ of atoms into a stable position ; la- 
bility and activity cease to exist. In further 
analogy to many cases of transformations of 
labile into stable compounds, enzymes are 
also ‘ killed’ by a certain amount of alkalies 
oracids. Different enzymes are resistant in 
very different degrees, however, not only to 
these agencies but also to other injurious 
compounds. This indicates either differ- 
ences in the nature of the labile atomic 
groups or, what appears more probable to 
the writer, different positions of the labile 
groups within the molecule. The closer to 
each other they are situated, the more 
easily the transformation to an inactive 
isomeric compound will take place. The 
greater the intensity of chemical energy at 
a given temperature the more activity is 
possible, and the more easily the point of 
destruction is reached. 
It seems highly probable that there exist 
two or even more labile groups in one mole- 
cule of an enzyme, since Jacobson observed 
that by a cautious application of heat their 
power of decomposing hydrogen peroxide 
* Organic chemistry abounds with interesting cases 
of this kind. Even the first synthesis of an organic 
compound, that of urea from ammonium cyanate, is 
due to such an interesting transformation. 
SCIENCE. 
959 
may be taken away, while their specific en- 
zymatic action may be retained.* 
A few instances will illustrate the differ- 
ences of resistance of enzymes: trehalmse 
is killed at 64° C., while inulase at about 70°, 
emulsian at 75—80°, diastase at 80-86°. The 
temperatures, however, vary considerably 
with the acid or alkaline reaction of the 
liquid, with the degree of concentration and 
with the presence of neutral salts, or of some 
organic neutral compounds. Furthermore, 
while pepsin resists at the ordinary tem- 
perature 2 per mille hydrochloric acid, 
trypsin, emulsin, diastase and papayotin 
are killed by less than 0.5 per mille.} 
On the other hand, pepsin is more easily 
destroyed by sodium carbonate than tryp- 
sin and rennet. Invertin is very easily de- 
stroyed by dilute alkali (Wrdblewski). 
Hydrogen sulphide easily kills the proteo- 
lytic enzyme of Micrococcus prodigiosus and 
Proteus vulgaris, not, however, that of Bacillus 
Milleri, nor pepsin, diastase or emulsin.{ 
The writer has observed that prussic acid 
of 25 per cent. kills diastase (but not tryp- 
sin) at the ordinary temperature within 12 
hours. Arsenious acid is reported to have 
no injurious effect upon enzymes, but in 
the writer’s opinion this question deserves 
further study. Certain alkaloids have also 
been observed to have a destructive ac- 
tion on enzymes. Quinine, 1 per cent. 
has an inhibitory effect on the action of 
* Zeitschrift f. physiol. Chem., Vol. 16, p. 340 (1892). 
Bourquelot assumes here the presence of an impurity 
with certain active properties which agrees with some 
recent tests of the writer. 
t Organic acids act less energetically. Thus Wré- 
blewski reports that invertin can resist even 4 per cent. 
acetic acid for some time. 
{Cf. Fermi, Archiv. f. Hygiene, Vol. 14, p. 15. 
Chem. Centralbl., 1894, I., p. 965. The writer has 
convinced himself that neither basic acetate of lead 
nor hydrogen sulphide, when applied for a short time 
in moderate quantities, injure diastase or trypsin, and 
therefore Wurtz’s method may well be applied for 
the preparation of these enzymes, especially from the 
pancreas gland. 
