ON THE NUCLEOTIDE SPECIFICITY OF THE POLYNUCLEOTIDE PHOSPHORYLASE OF THE CROWN-GALL TUMOR-INDUCING ORGANISM AGROBACTERIUM TUMEFACIENS

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Abstract
An investigation of the nucleotide specificity of the polynucleotide phosphorylase of Agrobacterium tumefaciens was undertaken, using the measurable increase in viscosity as an index of activity. It was found that ADP and CDP were polymerized readily and at approximately equal rates. The enzyme exhibited more moderate activity with UDP and was completely inactive with GDP. The ineffectiveness of the enzyme with mixtures of all four ribonucleoside diphosphates was traced to the ability of GDP to act as an inhibitor in the polymerization of the other diphosphates. Evidence is presented to show that the inhibition of poly A synthesis effected by GDP is competitive. On the basis of the results obtained it is concluded that the polynucleotide phosphorylase is not likely to be responsible for RNA synthesis in A. tumefaciens.

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