KG-501 (2-Naphthol-AS-E-phosphate) is used as a substrate in biochemical assays to investigate phosphatase enzyme activity, particularly in histochemical and cytochemical testing. This compound is hydrolyzed by phosphatase enzymes, yielding products that can be detected through optical or fluorescent methods, allowing for efficient analysis of enzyme distribution and activity in tissues or cells. Furthermore, it is utilized in scientific research to explore enzyme mechanisms and associated biochemical processes.