The RNase PH-like exosome proteins, PNPase and RNase PH all belong to the RNase PH family of RNases and are phosphorolytic exoribonucleases, meaning that they use inorganic phosphate to remove nucleotides from the 3' end of RNA molecules.
These RNase PH-related enzymes, PNPase and RNase PH, are part of the RNase PH family of RNases that utilize inorganic phosphate to remove nucleotides from the 3' end of RNA molecules, a process also carried out by other phosphorolytic exoribonucleases.