Used as a chromogenic substrate in enzymatic assays to detect and measure aminopeptidase activity, particularly for leucine aminopeptidase that cleaves the N-terminal amide bond of peptides. Upon hydrolysis by target enzymes, it releases β-naphthylamine, which can be coupled with diazonium salts to produce a visible colored precipitate, enabling easy detection in histochemical or microbiological testing. Commonly applied in clinical diagnostics and research to identify bacterial enzyme profiles and assess cellular enzyme activity in tissue samples.