Enzymatic Depolymerization of Polyadenylic Acid by Bovine Pancreatic Ribonuclease-A*

Abstract

Polyadenylic acid (poly A) was depolymerized with relatively high concentration of ribonuclease A (R Nase-A) to oligoadenylic acids having 2[image], 3[image]-cyclic phosphoryl groups as terminal nucleotides and adenosine 2[image], 3[image]-cyclic phosphate (A-cyclic-P). The latter was further hydrolyzed very slowly to adenosine 3[image]-phosphate. The mode of liberation of the intermediates and the final product was compared with that in the case of polyuridylic acid (poly U) with ordinarly concentration of the same enzyme. Effects of pH and salt concentration and influence of specific carboxymethylation of the enzyme on the reaction rate were compared when poly A and ribonucleic acid were used as substrates. The results indicated that both poly A and natural substrate should be degraded by RNase with the similar mode of reaction. The quantitative estimation of reaction rates of RNase against poly A, poly U, A-cyclic-P and uridine-2[image], 3[image]-cyclic phosphate was performed and the interactions of poly A with the enzyme were discussed.