Catalytic ribonuclease component of mitochondrial ribonuclease P, a complex composed of TRMT10C/MRPP1, HSD17B10/MRPP2 and PRORP/MRPP3, which cleaves tRNA molecules in their 5'-ends (PubMed:18984158, PubMed:25953853). The presence of TRMT10C/MRPP1, HSD17B10/MRPP2 is required to catalyze tRNA molecules in their 5'-ends (PubMed:25953853). Endonucleolytic cleavage of RNA, removing 5'-extranucleotides from tRNA precursor. Binds 2 Mg(2+) or Mg(2+) ions per subunit. Catalytic component of mitochondrial ribonuclease P, a complex composed of TRMT10C/MRPP1, HSD17B10/MRPP2 and PRORP/MRPP3 (PubMed:18984158). Down-regulated following mitochondrial unfolded protein response. Displays a distorted and non-productive active site that probably switches to a fully productive state only upon association with TRMT10C/MRPP1, HSD17B10/MRPP2 and pre-tRNA substrate. Degraded by LONP1 following mitochondrial unfolded protein response, probably leading to inhibit translation in mitochondrion. Belongs to the PPR family. P subfamily.