H-Thr-βNA (L-Threonine-β-naphthylamide) is a chromogenic substrate used in biochemical and clinical research. It is a synthetic peptide derivative where the amino acid L-threonine is linked to β-naphthylamine via an amide bond. This compound is specifically designed to be cleaved by certain proteolytic enzymes. Its primary application is as a substrate for the detection and assay of aminopeptidase activity, particularly for enzymes like aminopeptidase N (APN/CD13). Upon enzymatic hydrolysis, the amide bond is cleaved, releasing free β-naphthylamine. The released β-naphthylamine can then be coupled with a diazonium salt (e.g., Fast Garnet GBC) in a post-coupling reaction to produce an insoluble, colored azo dye, allowing for the visualization and quantification of enzyme activity. This makes it a valuable tool in histochemistry, cytochemistry, and in vitro diagnostic (IVD) reagent kits for studying enzyme localization and function in tissues and cells. Due to its specific role as an enzyme substrate for diagnostic and research purposes, it is classified as a biochemical reagent within the life sciences sector.