title: Two-component ribonucleotidyl transferase from Escherichia coli. III. Effect of nucleoside diphosphates on synthesis and pyrophosphorolysis of polyribonucleotides by the enzyme.
abstract: 1. The capacity of two-component ribonucleotidyl transferase to catalyze pyrophosphorolysis of polyribonucleotides is studied. 2. It is shown that nucleoside diphosphates (NDP), not being substrates for the enzyme, activate both the synthesis and pyrophosphorolysis of polynucleotides by the enzyme. The concentration of NDP is important for this effect: with an increase of NDP concentration the rate of synthesis increases and reaches a plateau at 10(-5) M NDP, while the rate of pyrophosphorolysis, attaining maximal values at 10(-5)--10(-3) M NDP, decreases with a further increase of NDP concentration. 3. The possible biological role of two-component ribonucleotidyl transferase is discussed.
mesh_terms: D011756:Diphosphates; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D010710:Phosphates; D011072:Poly U; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology*
chemical_list: D011756:Diphosphates; D010710:Phosphates; D012265:Ribonucleotides; D011072:Poly U; D012316:RNA Nucleotidyltransferases