Aminopeptidase A is a zinc-dependent metallopeptidase that selectively cleaves N-terminal Glu, or Asp residues from peptides. In mice, it is expressed on early B cells and on a subset of thymic cortical epithelial cells, but not on mature lymphocytes. Additionally, it is expressed on endothelial cells, intestinal epithelium, proximal renal tubules, and other non-hemopoietic tissues. In humans, angiotensin II is the the best-defined biologically active substrate of APA. Although its role in the immune response is still uncertain, its expression on renal cell carcinoma has been the focus of some cancer research studies.
