sentences:  Polynucleotide phosphorylase
  
  Polynucleotide Phosphorylase (PNPase) is a bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3'-terminal oligonucleotide polymerase activity.That is, it dismantles the RNA chain starting at the 3' end and working toward the 5' end.