Methionyl aminopeptidase (EC 3.4.11.18, methionine aminopeptidase, peptidase M, L-methionine aminopeptidase, MAP) is an enzyme. This enzyme catalyses the following chemical reaction Methionyl aminopeptidase (EC 3.4.11.18, methionine aminopeptidase, peptidase M, L-methionine aminopeptidase, MAP) is an enzyme. This enzyme catalyses the following chemical reaction This membrane-bound enzymatic activity is present in both prokaryotes and eukaryotes. Proteins possessing this activity include METAP1 and METAP2.