Used to measure STK (serine/threonine kinase) activity in human biological samples such as serum, plasma, or cell lysates. Commonly applied in research settings to study signaling pathways involved in cell growth, apoptosis, and metabolism. Helps in identifying dysregulation of kinase activity linked to diseases like cancer, diabetes, and neurodegenerative disorders. Enables high-throughput screening of potential kinase inhibitors in drug development. Provides a quantitative, sensitive, and specific method to monitor changes in STK levels in response to treatments or disease progression.