Characterization of an aminopeptidase in cerebrospinal fluidStructure elucidation of enzyme hydrolysis products of synthetic methionine-enkephalin by reversed-phase high-performance liquid chromatography and mass spectrometry

An aminopeptidase was found in canine cerebrospinal fluid via the presence of two products: Y, which has an [M + H]+ ion at m/z 182; and GGFM, which has an [M + H]+ ion at m/z 411. The linked scan at a constant ratio of the magnetic field to the electric field of the GGFM [M + H]+ ion at m/z 411 generates product ions at m/z 120, 150, 266, 297, 354, 357, and 411. That aminopeptidase was bestatin-sensitive (BSAP = bestatin-sensitive aminopeptidase), and had a half-time for disappearance of 60 min, maximum velocity of 1.08 nmol ml−1 min−1, and Michaelis constant of 0.26 nM.