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