The Enzymic Hydrolysis of Ribonucleic Acid and Its Relation to the Structure

It is noteworthy that most of the recent observations concerning the structure of ribonucleic acid (1) are in agreement regarding the presence of an as yet unknown labile linkage or linkages in the molecule. The information that has brought the facts to light has been obtained mostly by the use of enzymic methods. By the use of the enzyme ribonuclease, Allen and Eiler (2) have been able to show that the structure of ribonucleic acid from yeast differs from those proposed by Levene and Simms (3) or by Takahashi (4). The observed action of ribonuclease on ribonucleic acid is the liberation of an acidic group in the molecule. This group is thought to be of the nature of a secondary hydroxyl of organically combined phosphate. The action of ribonuclease may then be regarded as either (a) depolymerization or (b) fission of a cyclic structure. Thus, it stems reasonable that a study of the action of non-specific phosphatase preparations upon native ribonucleic acid and upon ribonucleic acid subjccted to the action of ribonuclease should yield information of eventual aid in solving tht: perplexing problem regarding the point of attack of ribonuclcase upon ribonucleic acid. To t)his end, a study of t,hc rate of liberation of inorganic phosphate when compared to the rate of liberation of the various constituent nucleosides should yield information regarding the heretofore unsolved problem of the relative positions of the mononucleotides in the tetranucleotide unit. Unfortunately, accurate quantitative procedures for the estimation of all four of the distinguishing derivatives (guanine, adenine, uracil, and cytosine) of the mononucleotides are not available. However, the results that were obtained for the measurement of the rate of liberation of guanosine and adenosine and their relation to the total liberated inorganic phosphate surpassed our expectations in offering support to t,he foregoing observations. The validit,y of these observations is shown in the following experiments.