IRAP (also known as placental leucine aminopeptidase, PLAP; leucyl cystinyl aminopeptidase, LNPEP; oxytocinase, Otase; vesicle protein of 165kD or vp165) belongs to the peptidase M1 family. IRAP (mouse 966aa, rat 1025 aa; human 1025 aa, chromosome 5q14.2-q15), a zinc-containing metalloprotein, degrades peptide hormones such as oxytocin, vasopressin, and angiotensin III, and inactivates Met-enkephalin and dynorphin. It is a type 2 membrane protein and is secreted due to proteolytic processing. IRAP is glycosylated and alternatively spliced to at least 3 isoform (1-15 aa missing in isoform 2 and 1-20 missing in isoform 3). The N-terminus (1-110 aa) is located in the cytoplasm, followed by TM domain (111-131 aa); the C-terminus (132-1025 aa) is extracellular. The secreted form is cleaved at 154-155 aa (processed secreted form 155-1025 aa). IRAP is highly expressed in placenta, heart, kidney, and small intestine. In brain, only the membrane form is found. The brain form is found to be 140kD due to differential glycosylation.