Removes the formyl group from the N-terminal Met of newly synthesized proteins. Requires at least a dipeptide for an efficient rate of reaction. N-terminal L-methionine is a prerequisite for activity but the enzyme has broad specificity at other positions. H2O + N-terminal N-formyl-L-methionyl-[peptide] = formate + N-terminal L-methionyl-[peptide] Binds 1 Fe(2+) ion. Belongs to the polypeptide deformylase family.