The Cytochrome P450 2S1 Colorimetric Cell-Based ELISA provides a lysate-free, convenient, and high-throughput approach for sensitive detection of CytochromeP4502S1 protein expression profile in cells. The kit can be used for measuring the relative amounts of CytochromeP4502S1 in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on CytochromeP4502S1.