Purification and characterization of polynucleotide phosphorylase from cucumber

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Abstract
Polynucleotide phosphorylase (polyribonucleotide:orthophosphate nucleotidyltransferase, EC 2.7.7.8) activity is found in many prokaryotes. Such enzymes were detected also in plants. The purification of polynucleotide phosphorylase from cucumber cotyledons and leaves is described. This enzyme is a complex of 3 subunits, possibly not identical, of about MW 50,000. Its enzymatic properties are similar to those of the tobacco enzyme. Unlike the prokaryotic enzymes, the plant enzyme shows activity in the absence of primer but is to various extents stimulated by various ribopolynucleotides or RNA. RNA-dependent RNA polymerase present at a low level and was separated from the much greater amount of polynucleotide phosphorylase, although some of the physical properties of the 2 enzymes are rather similar.