Guanine-uridylic acid

RNA contains the nucleotide bases adenine (A), uracii (Lf), guanine (G), and Cytosine (C). These bases are cox alently attached to the ribose phosphate to form nucleotides. The respective nucleotides ate called adenylic acid (A), uridylic acid (U), guanylic acid (G), and cytidylic acid (C>,... 

Up to this time, little attention had been paid to the possibility of phosphoamide links because, in 1910, Levene and Jacobs had shown that the (three) primary amino groups (of the purines and the cytosine) are presumably not substituted in the nucleic acid since they can be determined by van Slyke s method. However, in 1936, Bredereck hydrolyzed ribosenucleic acid (Boehringer) by boiling an aqueous solution of the substance, and isolated a very small amount of material which was described as amorphous, monobasic, and readily hydrolyzed to guanine and uridylic acid. He therefore decided it was a guanine-uridylic acid and assigned it the following structure. 

Gulland confirmed that guanine-uridylic acid is deaminated by nitrous acid, but thinks this takes place through rupture of a phospho-amide link. In support of this hypothesis he finds that phenyl-phos-... 

It should be a simple matter to decide between the two proposed structures by deaminating a larger sample of guanine-uridylic acid and determining whether the product is xanthine or xanthine-uridylic acid. 

ATP is not the only reactive triphosphate. Other puriife or pyrimidine bases (guanine, cytosine, hypoxanthine, uracil cf. Chapt. VII-1) may take the place of adenine in the molecule the corresponding triphosphates replace ATP in several metabolic reactions. We will mention two examples The uridylic acid system in the interconversion of carbohydrates and the cytidylic acid system in the synthesis of phosphatides. 

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