Mitochondria processing peptidase

This zinc-dependent enzyme [EC 3.4.24.59] of the peptidase M3 family catalyzes the hydrolysis of a peptide bond such that there is a release of an N-terminal octa-peptide at the second stage of processing of some proteins imported into the mitochondrion. The natural substrates are precursor proteins that already have been processed by the mitochondrial processing peptidase. 

Mitochondria arise by division and growth of preexisting mitochondria. Because they synthesize only a few proteins and RNA molecules, they must import many proteins and other materials from the cytoplasm. A mitochondrion contains at least 100 proteins that are encoded by nuclear genes.50,50a The mechanisms by which proteins are taken up by mitochondria are complex and varied. Many of the newly synthesized proteins carry, at the N terminus, presequences that contain mitochondrial targeting signals51-53 (Chapter 10). These amino acid sequences often lead the protein to associate with receptor proteins on the outer mitochondrial membrane and subsequently to be taken up by the mitochondria. While the targeting sequences are usually at the N terminus of a polypeptide, they are quite often internal. The N-terminal sequences are usually removed by action of the mitochondrial processing peptidase (MPP) in... 

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