The N-terminal methionine excision pathway is an essential process in which the N-terminal methionine is removed from many proteins, thus facilitating subsequent protein modification. In mitochondria, enzymes that catalyze this reaction are celled methionine aminopeptidases (MetAps, or MAPs; EC 3.4.11.18) (Serero et al., 2003 [PubMed 14532271]).