LC/MS analysis of peptides released from the rFAP digest of Met-α₂AP. (A) Total ion current (m/z = 350-1800 amu) of a control sample containing Met-α₂AP but lacking rFAP, showing only an internal standard peak (IS). (B) Total ion current of Met-α₂AP incubated with rFAP: IS, oxidized N-terminal 12 amino acid M1(o)-P12 peptide and the 12 amino acid M1-P12 peptide are observed. (C) Reconstructed ion currents (464.4-465.9 amu) of the rFAP-treated sample for the doubly charged ions represented the L4-P12 peptide, indicating the presence of an additional cleavage site within the N-terminal 12 residue peptide.