NUCLEIC ACIDS 141 



H0\ 

 0=P O.C 5 H 7 2 .0 5 H 4 ff 6 



HO/ | 



O 

 H0\ | 



O=P O . C 5 H C O . C 4 H 4 IS T 30 

 HO/ | 



O 

 H0\ | 



O^p_O . C 5 H C O.C 4 H 3 ^O 2 

 HO/ | 



O 

 / H0\ | 



0=P . C 5 II 7 2 . C 5 H 4 N- 5 O 

 HO/ 



Inosinic Acid and Guanylic Acid. These two substances were known 

 to be constituents of aiiirnaHissues before the constitution of yeast nucleic 

 acid had been proposed, and one of them was the subject of considerable 

 discussion because it was looked upon as a peculiar nucleic acid ; but both 

 are purine nucleotides of the class that has been discussed. 



Inosinic Acid. This substance was discovered by Liebig (a) (1847) 

 -in meat extract, and is now known to be a constant and characteristic con- 

 stituent of muscle tissue. By mild hydrolysis with mineral acid, it easily 

 decomposes into phosphoric acid pentose and hypoxanthine (Bauer, 1907) 

 (Xewberg and Brahu (a) (b) 1907, 1908). 



10 H 13 N 4 P0 8 + 2H 2 H 3 P0 4 + C 5 H 10 O 5 + C 5 H 4 X 4 O 



The substance is marked by the pentose, which is identical with the pentose 

 of yeast nucleic acid. The muscles of animals contain a nucleotide that 

 is unmistakably related to plant nucleic acid. (Levene and Jacobs (b) 

 1909.) The relation is not one of identity, for inosinic acid produces 

 hypoxanthine, where the nearest nucleotide of yeast nucleic acid produces 

 adenine. If the one nucleotide originates from the other (the plant food 

 of the animal), deaminization of the adenine group must occur somewhere. 

 Inosinic acid occupies a unique place in a discussion of yeast nucleic 

 acid, for, though it is not a nucleotide of yeast nucleic acid, it is the first 

 nucleotide whose constitution was solved, and the method of solution was 

 afterward applied to the purine nucleotides of yeast nucleic acid. Inosinic 

 acid is composed of three groups, and gives rise to three, and only three 

 substances by acid hydrolysis, viz., phosphoric acid, pentose and hypo- 

 xanthine. Theoretically, any one of the three groups may be the central 

 group connecting the other two. 



