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ENZYMES. 59
A. Danilewski first made the observation that concentrated solutions
of peptic cleavage products of protein substances separates an insol-
uble substance under the influence of rennin. This phenomenon has
since been observed by various investigators and the precipitate has
been called plastein by Sawjalow ’ and coagalose by Lawrow.2
The same
phenomenon is also obtained by other proteolytic enzymes.3
The plas-
tein* are considered by various investigators as synthetically formed
protein. The best proof for this view has been given by Henriques
and Gjalback. They show with the formol titration (see Chapter II)
that the nitrogen titratable by formol diminishes in the reaction and
they also found that the nitrogen precipitatable by tannic acid was
increased in the plastein formation. In a later work these authors
find that peptic cleavage products from proteins show a plastein for-
mation when under the influence of pepsin-hydrochloric acid in con-
centrated solution while in dilute solution the cleavage goes further and
they conclude from this that the process is reversible. Even protein
which has been partly split by acid or alkali shows a plastein formation
with pepsin-hydrochloric acid.4
The behavior of amygdalin and its cleavage products with enzymes
requires special mention. The cleavage takes place step by step as
follows
:
C:oH2 -NOi 1 +H2 = Cr,H5.CH(OCr) H11 05).CN+CGH12OG. . (1)
Amygdalin Mandelic acid nitrileglucoside Glucose
C6H5.CH(OC6H„05 ).CX + H2 = Cr,H5.CH™+C6H12 6 . . (2)
Uri
Mandelic acid nitrileglucoside Mandelic acid nitrile Glucose
CoH5 CH^ = CY,H5C<(°+KCX (3)
Mandelic acid nitrile Bcnzaldehyde Hydrocyanic acid
The entire process with the formation of the end products sugar,
benzaldehyde and hydrocyanic acid takes place under the influence of
emulsin from almonds. The first part of the process can be especially
brought about by the influence of yeast (Fischer)5
and the second and
third parts under the influence of prunase from the leaves of Pruneae.6
Of
1
Zeitschr. f. physiol. Chem., 54, ,119 (1907).
2
Ibid., .51, 1: 53, 1 (1907); 56, 343 (1908); 60, 520 (1909).
3
Kurajeff, Hofmeister’s Beitriige, 4, 476 (1904); Numbers, ibil., 4, 543 (1904).
4
Zeitschr. f. physiol. Chem., 71, 485 (1911); 81, 439 (1912).
5
Ber. d. d. chem. Gesellsch., 28, 1508 (1896).
6
H. E. Armstrong, E. F. Armstrong and Horton, Proc. Roy. Soc, 85, 359, 363,
370 (1912).
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