RNA-synthesizing enzymes in healthy and TMV-infected tobacco leaves. Partial purification and characterization to tobacco polynucleotide phosphorylase

Polynucleotide phosphorylase was partially purified from healthy and TMV-infected tobacco leaves. The enzyme catalyzed all three typical polynucleotide phosphorylase activities. It required Mg²⁺ or Mn²⁺ for the polymerization reaction and was stimulated by NH⁺₄, K⁺, sulfhydryl agents, and polyamines. The synthetic activity was enhanced in the presence of a primer and was completely inhibited by 0.1 mm inorganic orthophosphate. The enzyme was insensitive to freezing. An approximate molecular weight of 150,000 was estimated.