L-Arginine p-nitroanilide dihydrochloride is primarily used as a substrate in enzymatic assays to study the activity of arginine-specific proteases, such as trypsin and other serine proteases. It serves as a chromogenic compound, where the cleavage of the p-nitroanilide group by the enzyme results in the release of p-nitroaniline, which can be easily detected spectrophotometrically due to its yellow color. This makes it a valuable tool in biochemical research for quantifying enzyme activity and kinetics. Additionally, it is employed in diagnostic applications to measure protease levels in biological samples, aiding in the study of protease-related diseases and conditions. Its specificity and ease of detection make it a preferred choice in both academic and industrial laboratories for enzyme characterization and inhibitor screening.