Polyribonucleotide nucleotidyltransferases catalyze template-independent polymerization of RNA from nucleotide diphosphates as well as the reverse reaction, the phosphorolysis of RNA polynucleotides. This activity is found within the bifunctional enzyme PNPase. While PNPase can act as a polynucleotide or poly(A) polymerase in bacteria, it predominantly functions as a 3' to 5' exoribonuclease in most organisms, playing critical roles in RNA processing and degradation. (Adapted from PMID:30307990.)

polyribonucleotide nucleotidyltransferase (2.7.7.8)