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50 GENERAL AND PHYSICO-CHEMICAL.
aqueous solutions, and even at ordinary temperature the enzymes are
gradually decomposed. In general the enzymes lose their activity by
heating for a short time to 70° C. Madsen and Walbum have followed
this process at different temperatures and found that the decomposition
of trypsin, pepsin and rennin at given temperatures proceeds mono-
molecularly, i.e., that the velocity of reaction at every moment is pro-
portional to the concentration of the enzyme (page 34). l
The readiness
with which an enzyme is decomposed is nevertheless to a great extent
dependent upon the presence of other bodies (page 54).
Certain enzymes are also sensitive to light. According to Schmidt-
Nielsen 2
rennin is injured by light and in particular, by the ultra-violet
rays. The experiments of Jodlbauer and Tappeiner 3
with invertin
have led to the same results; the visible rays can also in some cases
(peroxidase, haemase) in the presence of oxygen or certain fluorescent
substances exert an injurious action.4
According to Schmidt-Nielsen 5
the weakening in the rennin under
the influence of light proceeds like a monomolecular reaction.
Experiments on the cataphoresis of enzymes have been made by
Bierry, Henry and Schaeffer 6
as well as by Michaelis. . These
investigators found that saccharase migrates to the anode. Michaelis 7
found that the migration direction of other enzymes was dependent upon
the reaction, namely in faintly acid reaction they moved to the cathode
and in faintly alkaline reaction to the anode. Recently Pekelharing
and \Y. E. Ringer 8 have observed that the migration direction of pig
pepsin was very materially influenced by the addition of small amounts
of proteoses. From what was previously stated (page 20) the saccharase
must therefore have a negative charge. As Michaelis,9
has on the other
hand, found that the saccharase can be adsorbed by the positively
charged aluminium hydrate and not by the negatively charged kaolin,
he concludes that the formation of adsorption compounds, at least in
certain cases, depends upon an opposed electric charge of the two com-
ponents.
1
Arrhenius, Immunochemie, Leipzig, 1907, 58.
2 Hofmeister’s Beitrage, 5, 355(1904); 8,481(1906); Zeitschr. f. physiol. Chem., 58,
233 (1908).
Arch. f. klin. Med., 87, 373 (1906).
* Bioch. Zeitschr., 8, 61 and 84 (1908). See also Agulhon, Compt. rend., 153, 979
(1911;.
5
Zeitschr. f. physiol. Chem., 58, 232 (1908).
•
Compt. rend. boo. biol., 68, 226 (1907).
7
Bioch. Zeitschr., 16, SI, 486; 17, 231 (1909).
8Zeitsfhr. f. physiol. Chem., 75, 282 (1911). .
9 Bioch. Zeitchr., 10, 299 (1908).
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