CD13

CD13, also known as aminopeptidase N (APN), is a membrane-bound zinc-dependent metalloprotease encoded by the ANPEP gene. It functions to cleave N-terminal amino acids from peptide substrates, contributing to peptide processing, regulation of signaling peptides, and roles in antigen presentation. It belongs to the M1 family of zinc metalloproteases and contains the characteristic zinc-binding motif necessary for catalytic activity.

Expression of CD13 is broad but is most prominent on myeloid lineage cells such as granulocytes and monocytes. It is also found on various epithelial tissues, including kidney and small intestine, as well as on endothelial cells. In clinical hematology, CD13 is used as a surface marker in immunophenotyping to help identify myeloid cells and characterize subsets of acute myeloid leukemia and related disorders, often in combination with other markers.

In disease and biology, CD13 can influence processes involved in tumor progression, including invasion and angiogenesis, though its role is context-dependent and varies among tumor types. As an enzyme, its activity can affect the local peptide milieu, with potential consequences for cell signaling and microenvironment interactions.

Clinical and therapeutic relevance includes CD13’s role as a receptor for certain pathogens, such as human coronavirus 229E, and its tractability as a drug target. Inhibitors of aminopeptidase N, such as bestatin (ubenimex), have been explored for immunomodulatory and anti-tumor effects in research and clinical settings. Ongoing studies continue to define its utility in diagnostics and targeted therapies.