LNPEP, also known as insulin-responsive aminopeptidase (IRAP), was initially identified as an abundant protein that is associated with specialized endosomes termed GLUT4 storage vesicles (GSVs) in adipocytes. The luminal domain of LNPEP contains an aminopeptidase activity that is involved in peptide hormone processing and antigenic peptide processing. LNPEP is also a key regulator of GLUT4 trafficking by controlling the sorting of GLUT4 from endosomes to the GSVs.Synonyms: Cystinyl aminopeptidase, EC=3.4.11.3, IRAP, Insulin-regulated membrane aminopeptidase, Insulin-responsive aminopeptidase, LNPEP, Leucyl-cystinyl aminopeptidase, OTASE, Oxytocinase, P-LAP, Placental leucine aminopeptidase