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PROTEOSES AND PEPTONES. 129
We formerly designated as peptones those protein bodies which are
readily soluble in water and which are not coagulated by heat, whose
solutions are precipitated neither by nitric acid, nor by acetic acid and
potassium ferrocyanide, nor by NaCl and acid.
The reactions and properties which the proteoses and peptones have
in common were formerly considered as the following: They all
give the color reactions of .the proteins, but with the biuret test they give
a more beautiful red color than the ordinary proteins. They are pre-
cipitated by ammoniacal lead acetate, by mercuric chloride, tannic, phos-
photungstic, and phosphomolybdic acids, by potassium-mercuric iodide
and hydrochloric acid, and also by picric acid. They are precipitated
but not coagulated by alcohol, that is, the precipitate obtained is soluble
in water even after being in contact with alcohol for a long time. The
proteoses and peptones also have a greater diffusive power than native
proteins, and the diffusive power is greater the nearer the questionable
substance stands to the final product, the now so-called true peptone.
These old views have gradually undergone an essential change. After
Heynsius’ * observation that ammonium sulphate was a general pre-
cipitant for proteins, and for peptones in the old sense, Kuhne and his
pupils 2
proposed this salt as a means of separating proteoses and pep-
tones. Those products of digestion which separate on saturating their
solution with ammonium sulphate, or can indeed be salted out at all,
are considered, by Kuhne and also by most of the modern investigators,
as proteoses, while those which remain in solution are called peptones
or true peptones. These true peptones are formed in relatively large
amounts in pancreatic digestion, while in pepsin digestion they are formed
only in small quantities or after prolonged digestion.
According to Schutzenberger and Kuhne 3
the proteins yielded
two chief groups of new protein bodies wdien decomposed by dilute
mineral acids or wr
ith proteolytic enzymes; of these the anti group shows
a greater resistance to further action of the acid and enzyme than the
other namely, the hemi group. These two groups are, according to
KtiHNE, united in the different proteoses, even though in various relative
amounts, and each proteose contains the anti as well as the hemi group.
The same is true for the peptone obtained in pepsin digestion, hence he
calls it amphopeptone. In tryptic digestion a cleavage of the ampho-
1
Pfluger’s Archiv, 34.
2
See Kuhne, Yerhandl. d. naturhistor. Vereins zu Heidelberg (N. F.), 3; J. Wenz,
Zeitschr. f. Biologie, 22; Kuhne and Chittenden, Zeitschr. f. Biologie, 22; R. Neu-
meister, ibid., 23; Kuhne, ibid., 29.
3
Schutzenberger, Bull, de la Soc. chimique de Paris, 23; Kuhne, Yerhandl. d.
naturhist. Vereins zu Heidelberg (N. F.), 1, and Kuhne and Chittenden, Zeitschr. f.
Biologie, 19. See also Paal, Ber. d. deutsch. chem. Gesellsch., 27.
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