Hippuryl-L-phenylalanine is primarily used as a substrate in enzymatic assays to measure the activity of angiotensin-converting enzyme (ACE). This enzyme plays a critical role in regulating blood pressure, and the compound helps in assessing ACE inhibitors, which are drugs used to treat hypertension and heart failure. Additionally, it serves as a tool in biochemical research to study peptide hydrolysis and enzyme kinetics. Its application extends to diagnostic laboratories for evaluating conditions related to the renin-angiotensin system.