Metalloendopeptidase of the mitochondrial matrix that functions in peptide cleavage and degradation rather than in protein processing . Has an ATP-independent activity . Specifically cleaves peptides in the range of 5 to 65 residues. Shows a preference for cleavage after small polar residues and before basic residues, but without any positional preference . Degrades the transit peptides of mitochondrial proteins after their cleavage . Also degrades other unstructured peptides. It is also able to degrade amyloid-beta protein 40, one of the peptides produced by APP processing, when it accumulates in mitochondrion. It is a highly efficient protease, at least toward amyloid-beta protein 40. Cleaves that peptide at a specific position and is probably not processive, releasing digested peptides intermediates that can be further cleaved subsequently.