Protein kinase A (PKA) regulates multiple signal transduction events via protein phosphorylation and is integral to all cellular responses involving the cyclic AMP second messenger system. KT 5720 is one of a family of compounds synthesized by the fungus Nocardiopsis sp. It blocks PKA signaling through competitive inhibition of ATP with a Ki value of 60 nM. Reported IC50 values vary widely depending upon ATP concentration tested and can range from 56 nM (low ATP) to 3 μM (physiologic ATP). Non-specific effects of KT 5720 include inhibition of phosphorylase kinase, PDK1, MEK, MSK1, PKBα, and GSK3β at concentrations as effective as or more potent than that for inhibition of PKA.
