CD13 is a myeloid differentiation molecule expressed on committed myeloid progenitors, granulocytes, monocytes, and leukemic cells of myeloid origin. It is also expressed on nonhematopoietic cells including fibroblasts, renal proximal tubule, and small intestine brush-border membrane. The gene for CD13 has recently been cloned the cDNA sequence shows that CD13 is the metalloprotease aminopeptidase N. Biochemical studies have shown that CD13 is a 150- kDa glycoprotein, which exists as a 130- kDa intracellular precursor form. This 130- kDa precursor molecule is post-translationally modified in the Golgi apparatus to produce the 150- kDa mature cell surface form of the molecule.Synonyms: ANPEP, APN, Alanyl aminopeptidase, Aminopeptidase M, Aminopeptidase N, Microsomal aminopeptidase, Myeloid plasma membrane glycoprotein CD13, PEPN, gp150