Sodium 4-Nitrophenylacetate is primarily used in biochemical research as a substrate for enzyme assays. It is particularly useful in studying the activity of esterase enzymes, which catalyze the hydrolysis of ester bonds. When the compound is hydrolyzed by esterases, it releases 4-nitrophenol, a yellow-colored product that can be easily measured spectrophotometrically. This allows researchers to quantify enzyme activity and kinetics in a straightforward and reliable manner. Additionally, it is employed in diagnostic applications to detect esterase activity in biological samples, aiding in the identification of specific enzymes or the assessment of enzyme inhibition. Its stability and ease of detection make it a valuable tool in both academic and clinical laboratories.