Inhibition of Polynucleotide Phosphorylase by Degraded Ribonucleic Acid : its Reversal by Various Agents

Abstract

STUDIES in this Laboratory have shown that non-dialysable commercial yeast ribonucleic acid and alkaline degraded polyadenylic acid strongly inhibit the polymerization of polyadenylic acid by polynucleotide phosphorylase from M. lysodeikticus¹. Substantial inhibition also occurs with ribonucleic acid from B. subtilis partially digested with ribonuclease. The reaction of the inhibitor with the enzyme preparation is slow and may require up to 30 min. for completion. If the substrate, adenosine diphosphate, is added simultaneously with the ribonucleic acid the rate and extent of inhibition is reduced considerably. Concentrations of yeast ribonucleic acid as low as 10⁻⁷ M (phosphate) can give up to 100 per cent inhibition of synthesis of polyadenylic acid. However, in the presence of these inhibitors the rate of polymerization is autocatalytic and shows a significant lag, the extent of which depends upon the inhibitor concentration. Both the inhibition and the autocatalytic character of the rate-curve can be reduced or abolished by the addition of acridine orange, a B. subtilis ribonucleic acid preparation, or polyadenylic acid (Fig. 1).