Degradation of Yeast Ribonucleic Acid by Polynucleotide Phosphorylase from <I>Azotobacter agilis (vinelandii)</I>:II. Effect of Terminal Phosphate of Ribonucleic Acid and Effect of Ribonucleoside 5'-Diphosphate

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Causes for the low reactivity of yeast RNA as compared with Poly A in the degradation by polynucleotide phosphorylase [EC 2.7.7.8] from Azotobacter agilis were studied. Since the modified commercial RNA treated with phosphatase [EC 3.1.3.1] was phosphorolyzed and arsenolyzed eighteen and sixteen times, respectively, faster than the untreated commercial RNA and since the initial rate obtained for the treated. RNA was even higher than that obtained for Poly A, the phosphomonoester end groups of the RNA were considered to be mainly responsible for the low reactivity. The rapid decrease of reaction rate in the later stage of the degradation of commercial RNA was ascribed to the product inhibition. The product, ADP, GDP or CDP (each 0.3mg./ml.) and a mixture of ADP, GDP, CDP and UDP (each 0.3mg./ml.) caused 15% and 60% inhibition, respectively, of the phosphorolysis of dephosphorylated commercial RNA (1.0mg./ml.). The RNA with a terminal phosphate, which remained unattacked, also inhibited the degradation. On the other hand, the degradation rate of highly polymerized RNA was not affected by the phosphatase treatment. The hydrogen bond in the structure of this RNA seems, therefore, to be responsible for the low degradation rate.

Journal

  • J Biochem (Tokyo)

    J Biochem (Tokyo) 62 (6), 673-678, 1967

    The Japanese Biochemical Society

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