Enzymatic activities of the two VAP-1 isoforms.

The SSAO-activity and substrate specificities of VAP-1 and VAP-1Δ3 were defined by a fluorometric assay from lysed transfectants. (A) HEK293 cells transfected with VAP-1. (B) HEK293 cells transfected with VAP-1Δ3 (C) HUVECs infected with VAP-1 (D) HUVECs infected with VAP-1Δ3. The final concentrations of all substrates were 1 mM. MA methylamine; BZ benzylamine; TYR p-tyramine; TRYPT tryptamine; PEA 2-phenylethylamine; HIS histamine. The results are expressed as nmol/mg/h+standard deviation (SD) (n = 3). (E) The structure of dimeric VAP-1 (PDB code 1US1; Airenne et al., 2002), viewed from the side of the carboxy-terminus along the two-fold axis. Both monomers are drawn in rainbow colors from blue amino-termini to red carboxy-termini. The amino acids missing from VAP-1Δ3 (aa 634-761) are illustrated as gray spheres of different shades. The picture was generated with PyMol [54].