182 THE PROTEIN 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 nudeases. Micro-organisms can also 

 bring about a more or less deep cleavage of the nucleic acids (ScniT- 



TENHELM and SCHROTER 1 ). 



LEVENE and MEDIGRECEANU 2 differentiate between three kinds of 

 nucleases namely, nucleinases, nucleotidases and nucleosidases. The 

 nudeinases, 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 nucleoticles. 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 adenosin-deamidase which deami- 

 dizes the still combined adenine. On the contrary the same organ also 

 contains a guanase which deamidizes 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, CioHia^POg 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, ibid., 39; Fr. Sachs, " 1st die 

 Nuklease mit dem Trypsin ideritisch? " Inaug. -Dissert, Heidelberg, 1905; Schitten- 

 helm and Schroter, f. physiol. Zeitschr. Chem., 41. 



2 Journ. of biol. Chem., 9. 



3 Journ. of biol. Chem., 9. 



4 Zeitschr. f. physiol. Chem., 77. 



5 Liebig, Annal. d. chem. u. Pharm., 62; Haiser, Monatsh. f. chem., 16; Neuberg 

 and Brahn, Biochem. Zeitschr., 5 and Ber. d. d. chem. Gesellsch., 41, p. 3376; Bauer 

 Hofmeister's Beitrage, 10; Levene and Jacobs, Ber. d. d. chem. Gesellsch., 41, p. 2703. 



