Leukocyte-derived arginine aminopeptidase (LRAP), also known as endoplasmic reticulum-aminopeptidase 2 (ERAP2), is the second identified aminopeptidase localized in the in the lumenal side of endoplasmic reticulum (ER) processing antigenic peptides presented to major histocompatibility complex (MHC) class I molecules. It is a 960-amino acid protein with significant homology to placental leucine aminopeptidase and adipocyte-derived leucine aminopeptidase. LRAP preferentially hydrolyzes the basic residues Arg and Lys, and contains the HEXXH(X)18E zinc-binding motif, which is the characteristic of the M1 family of zinc metallopeptidases which also includes PILS/ARTS1/ERAP1 and LNPEP/PLAP. Induced by interferon-gamma, LRAP is able to trim various MHC class I antigenic peptide precursors.