Aminopeptidase A, also designated APA, gp160 human kidney differentiation antigen, glutamyl aminopeptidase, or enpep, is a differentiation-related kidney glycoprotein. As a cell surface, zinc-dependent metalloprotease, Aminopepti-dase A specifically cleaves amino-terminal acidic residues from peptide substrates such as Angiotensin II. APA is expressed on the surface of epithelial cells of the glomerulus and proximal tubule cells of the human nephron, where it may mediate the constitutive trafficking of Glut4-containing vesicles. These Glut4-containing vesicles are tissue-specific secretory-like microsomal structures that mediate insulin-dependent translocation of GLUT4 to the cell surface in fat and muscle cells. Mutations in the gp160/APA gene, including loss of protein expression or enzymatic activity, occur in 20% of primary clear cell renal carcinomas.