L-Leucine-7-amido-4-methylcoumarin hydrochloride is primarily used in biochemical research as a fluorogenic substrate for proteolytic enzymes, particularly leucine aminopeptidase. Its application lies in the detection and quantification of enzyme activity, where the compound is cleaved by the enzyme to release a fluorescent product, 7-amino-4-methylcoumarin. This fluorescence can be measured to assess enzyme kinetics or screen for enzyme inhibitors. It is also employed in cell biology studies to monitor intracellular protease activity, aiding in understanding cellular processes and disease mechanisms. Additionally, it serves as a tool in drug discovery to evaluate the efficacy of therapeutic agents targeting specific proteases.