Leu-pNA, Chromogenic Substrate is a substrate for aminopeptidase, a zinc dependent enzyme that assists in the digestion of proteins. The compound has been used in an ELISA assay to detect biological functionality of chicken aminopeptidase produced by E. coli. The compound has also been used to characterize the native IRAP (placental leucine aminopeptidase). Leu-pNA, Chromogenic Substrate is documented for use with pure samples as well as cell extracts in vitro. Leu-pNA, Chromogenic Substrate is a substrate of CD13.