Zinc phosphodiesterase, which displays mitochondrial tRNA 3'-processing endonuclease activity. Involved in tRNA maturation, by removing a 3'-trailer from precursor tRNA. Associates with mitochondrial DNA complexes at the nucleoids to initiate RNA processing and ribosome assembly. Endonucleolytic cleavage of RNA, removing extra 3' nucleotides from tRNA precursor, generating 3' termini of tRNAs. A 3'-hydroxy group is left at the tRNA terminus and a 5'-phosphoryl group is left at the trailer molecule. Homodimer. Interacts with PTCD1. Mainly mitochondrial. Belongs to the RNase Z family.