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182 THE PJHOTEIN SUBSTANCES.
The proteolytic enzymes, such as pepsin and trypsin, decompose the
nucleoproteins more or less; the nucleic acids are apparently not
split by these enzymes or at least not as far as phosphoric acid and
purine bases. Such a cleavage can, on the contrary, be brought about
by erepsin (Nakayama) or by other closely allied enzymes found in
various organs which have been called nucleases. Micro-organisms can also
bring about a more or less deep cleavage of the nucleic acids (Schit-
TENHELM and SCHROTER 1
).
Levene and Medigreceantt 2
differentiate between three kinds of
nucleases namely, nucleinases, nucleotidases and nucleosidases. The
nucleinases, which are found in the pancreatic juice and all organs
investigated, but not. in gastric juice, acts only upon the complex nucleic
acids and splits them into nucleotides. The nucleotidases, which, with
the exception of the gastric and pancreatic juices, occurs all over and
especially in the intestinal mucosa, split the simple nucleic acids (mono-
nucleotides) into phosphoric acid and the corresponding nucleoside
(purine pentoside). The nucleosidases, which are not found in the gastric,
pancreatic or intestinal juices, nor in the blood or the pancreas but in
other organs, split the nucleosides into purine base and pentose. It is
unknown how the cleavage of the pyrimidine and hexose complexes
of the nucleic acids is brought about.
According to W. Jones 3 the purine bases of the nucleic acids can be
deamidized without being previously split off as free base from the acid.
Thus the pig-pancreas contains an adencsin-deamidase which deami-
dizes the still combined adenine. On the contrary the same organ also
contains a guanase which deamiclizes the free guanine but does not
contain a guanosine deamidase. The pig liver, in which only traces of
guanase occur, contain on the contrary a guanosine-deamidase. Recent
investigations of Schittenhelm and K. Wiener 4
show that we must
also admit of nucleoside-deamidases besides purine deamidases.
Inosinic Acid, C10H13N4PO8 was first isolated by Liebig from the
flesh of certain animals and then closely studied by Haiser. It is obtained
from beef extracts, and according to the investigations of Neuberg and
Brahn, Fr. Bauer, and Levene and Jacobs it is a simple nucleic acid.5
1
Nakayama, Zeitschr. f. physiol. Chem., 41; Iwanoff, iUd., 39; Fr. Sachs, " 1st die
Nuklease mit ’lorn Trypsin identisch? " Inaug.-Dissert, Heidelberg, 1905; Schitten-
helm and Schroter, f. physiol. Zeitschr. Chem., 41.
2
Journ. of biol. Chem., 9.
3
Journ. of bio!. Chem., 9.
4
Zeitschr. f. physiol. Chem., 77.
Liebig, Annul, d. chem. u. Pharm., 62; Haiser, Monatsh. f. chem., 16; Neuberg
and Brahn, Biochem. Zeitschr., 5 and Ber. d. d. chem. Gesellsr-h., 41, p. 3376; Bauer
Hofmeister’s Beitriige, 10; Levene and Jacobs, Ber. d. d. chem. Gesellsch., 41, p. 2703.
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