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PROTEOSES AND PEPTONES. 133
views of Kuhne are not in all points correct still the fact remains that
under certain circumstances I he protein can be split into fractions, of which
the hemi group is further easily decomposed by enzyme action while the
other, the anti group, is very much more resistant to such action. It
also seems as if the first group is characterized by a larger content of
tyrosine, tryptophane and the latter by its content of glycocoll, phenyl-
alanine and proline.
By the use of the methods specially worked out by the Hofmeister
school, of fractionally salting out with ammonium sulphate or zinc sul-
phate or also by Siegfried’s iron-alum method, numerous attempts to
separate the various proteoses and peptones have been made.1
Not
only have we learned by these methods of a larger number of proteoses,
but our older conception of the products formed primarily has been
materially modified. Immediately at the commencement of diges-
tion, even in peptic digestion, a splitting of the protein molecule into
several complexes takes place. In opposition to the view of Huppert,2
that
the proteoses, in pepsin digestion, are always derived from the primarily
formed acid albuminate, Pick and Zunz have shown that several pro-
teoses, as well as acid albuminate, appear as primary products at the
commencement of the digestion. According to Goldschmidt 3
a splitting
off of proteoses and the formation of acid albuminate takes place simul-
taneously by the action of dilute acids alone. Besides the proteoses
we also have, according to Zunz and Pfaundler, even at the beginning,
other primary bodies, which cannot be salted out and which do not
give the biuret reaction, but are in part precipitated by phosphotungstic
acid. These little-known products seem to be intermediate between
the peptones and the amino-acids, and they correspond probably to
the polypeptide bodies obtained by Fischer and Abderhalden in tryptic
digestion.
By fractional precipitation of Witte’s peptone with ammonium sulphate
Pick has obtained various chief fractions of proteoses. The first contains the
proto- and heteroproteoses whose precipitation limit lies at 24-42 per cent satu-
ration with ammonium sulphate solution, i.e., the presence of 24-42 cc. of the
saturated ammonium sulphate solution in 100 cc. of the liquid. Then follows
a fraction A at 54-62 per cent saturation, then a third fraction B. with 70-95
per cent saturation, and finally fraction C, which precipitates from the saturated
solution on acidification with sulphuric acid saturated with the salt.
1
Umber, Zeitschr. f. physiol. Chem., 25; Alexander, ibid., 25; Pfaundler, ibid.,
30; Zunz, ibid., 28, and Hofmeister’s Beitriige, 2; Pick, ibid., 2, and Zeitschr. f. physiol.
Chem., 24 and 28; Siegfried, see footnote 3, p. 136.
2
Schiitz and Huppert, Pfliiger’s Arch., 80.
* F. Goldschmidt, Ueber die Einwirkung von Sauren auf Eiweisstoffe, Inaug.-
Diss. Strassburg, 1898.
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