The Tryptophan Hydroxylase Colorimetric Cell-Based ELISA Kit is a convenient, lysate-free, high throughput and sensitive assay kit that can detect TryptophanHydroxylase protein expression profile in cells. The kit can be used for measuring the relative amounts of TryptophanHydroxylase in cultured cells as well as screening for the effects that variuos treatments, inhibitors (ie siRNA or chemicals), or activators have on TryptophanHydroxylase.