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ENZYMES. 65
which is difficult to digest (Delezenne and Pozerski,1
Vernon,2
Qompel and Henri,3 Hedin 4
).
At this time we must also mention the retarding action which the
proteolytic primary cleavage products (proteoses, peptones) exert upon
digestion. These products are further split; a part of the enzyme is
combined with the products and in this way prevented from dissolv-
ing new protein (Hedin).5
The retarding power of proteoses and pep-
tones upon rennin action is probably similar to the above.6
Finally, the end products of enzymotic activity i.e., bodies which
cannot be further split by the enzyme, have also a retarding action on
the enzyme action. That the inversion of cane-sugar is retarded by
invert sugar has been claimed by many (Henri,7
A. J. Brown,8 Baren-
drecht,9
Armstrong 10
), and indeed Barendrecht claims that glucose
as well as fructose has a retarding action, and that galactose has an
even stronger retarding action than the direct cleavage products of cane-
sugar. H. E. and E. F. Armstonng 11
found that saccharase, maltase and
lactase are retarded by just those varieties of sugar which are produced
by their activity. The accumulation of the amylolytic cleavage prod-
ucts have according to Sh. Lea,12
a retarding action upon saliva.
The retarding action of amino-acids upon the decomposition of glycyl-
Z-tyrosine by yeast-press juice has recently been studied by Abderhalden
and Gigon.13
They found that cleavage of peptides is retarded by
those optically active amino-acids which occur in the proteins. This
result is remarkable in consideration of the observations of Fischer
and Abderhalden that only those polypeptides were split by pancreatic
juice which are composed of natural optically active amino-acids (page 62).
The retardation of the action of papain by egg protein and by serum, which
is prevented by heating or action of hydrochloric acid, as shown by the investiga-
tions of Delezenne, Mouton and Pozerski as well as by Jonescu and Sachs u
is a peculiar behavior.
1
Compt. rend. soc. biol., 55, 935 (1603).
2
Journ. of Physiol., 31, 495 (1904).
3
Compt. rend. soc. biol., 58, 457 (1906).
4
Zeitschr. f. physiol. Chem., 52, 422 (1907).
5
Zeitschr. f. physiol. Chem., 52, 422 (1907).
6
Ibid., 46, 307.
7
Zeitschr. f. physik. Chem., 39, 194 (1901).
8
Journ. Chem. Soc, 81, 382 (1902).
9
Zeitschr. f. physik. Chem., 49, 456 (1904).
10 Proc. Roy. Soc. (ser. B), 73, 516 (1904).
11 Ibid., 79,360 (1907).
12
Journ. of Physiol., 1911.
13
Zeitschr. f. physiol. Chem., 53, 251 (1907).
14 Delezenne, Mouton and Pozerski, Compt. rend., 142; Jonescu, Bioch. Zeitschr.,
2; Sachs, Zeitschr. f. physiol. Chem., 51, 488 (1907).
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