Aminopeptidase P--a cell-surface antigen of endothelial and lymphoid cells: catalytic and immuno-histotopical evidences

The physiological function of the GPI-anchored ectoenzyme aminopeptidase P (APP) is still elusive. Most researchers suppose that this enzyme inactivates biologically active peptides like bradykinin, neuropeptide tyrosine (NPY) and others (Vanhoof et al., 1995). We demonstrate by immunohistology with a specific antibody raised in rabbits and measurement of enzymatic activity in suspensions and of confluent monolayers on microscopic coverslips ('monolayer kinetics') that APP is a cell surface enzyme (ectoenzyme) of endothelial and lymphoid cells.