RNase PH is a tRNA nucleotidyltransferase, present in archaea and bacteria, that is involved in tRNA processing.

Contrary to hydrolytic enzymes, it is a phosphorolytic enzyme, meaning that it uses inorganic phosphate as a reactant to cleave nucleotide-nucleotide bonds, releasing diphosphate nucleotides.

The active structure of the proteins is a homohexameric complex, consisting of three ribonuclease (RNase) PH dimers.

The part of another larger protein with a domain that is very similar to RNase PH is called an RNase PH domain (RPD).

Two highly related exoribonuclease complexes: