Protein phosphorylation is one of the most important post-translational_x000D_modification processes. Phosphorylation is reversibly regulated by Protein Kinases (PKs) and_x000D_Protein Phosphatases (PTPs). PTP1B (PTPN1) is known to catalyze dephosphorylation of_x000D_insulin receptor kinases and plays a critical role in insulin signaling. The PTP1B Colorimetric_x000D_Assay Kit is designed to measure PTP1B activity for screening and profiling applications, in a_x000D_homogeneous assay with no time-consuming washing steps. The PTP1B Colorimetric Assay Kit is optimized for both_x000D_continuous and end-point assay formats.