Phosphorolysis of oligoribonucleotides by polynucleotide phosphorylase.

This reversible reaction has been demonstrated With enzyme preparations from Azotobacter trinelundii (1, 2) and Escherichia coli (3). In the forward direction the enzyme catalyzes the formation of polyribonucleotides similar in structural details to natural RNA1 (5-8). In the reverse reaction polyribonucleotides are phosphorolyzed to yield nucleoside diphosphates. The phosphorolysis of synthetic polymers made by the enzyme and the phosphorolysis of ribonucleic acids isolated from various natural sources have been studied by Ochoa and coworkers with the A. VineZundii enzyme (2, 9), by Littauer and Kornberg with a preparation from E. coli (3), and by Heppel.2 Highly polymerized RNA preparations were phosphorolyzed at slower rates than the synthetic polymers; however, commercial RNA and RNA “core,” the limit polynucleotides obtained after exhaustive