Cell
signaling is governed by dynamic changes in kinase and phosphatase
activities, which are difficult to assess with discontinuous readout
methods. Here, we introduce an NMR-based reporter approach to directly
identify active kinases and phosphatases in complex physiological
environments such as cell lysates and to measure their individual
activities in a semicontinuous fashion. Multiplexed NMR profiling
of reporter phosphorylation states provides unique advantages for
kinase inhibitor studies and reveals reversible modulations of cellular
enzyme activities under different metabolic conditions
